| Author | Tokens | Token Proportion | Commits | Commit Proportion |
|---|---|---|---|---|
| Peter Zijlstra | 11770 | 26.82% | 245 | 20.40% |
| Vincent Guittot | 6348 | 14.46% | 119 | 9.91% |
| Mel Gorman | 3237 | 7.37% | 69 | 5.75% |
| Rik Van Riel | 2763 | 6.29% | 55 | 4.58% |
| Paul Turner | 1806 | 4.11% | 34 | 2.83% |
| Ingo Molnar | 1665 | 3.79% | 66 | 5.50% |
| Josh Don | 1330 | 3.03% | 11 | 0.92% |
| Vincent Donnefort | 808 | 1.84% | 12 | 1.00% |
| Huang Ying | 652 | 1.49% | 7 | 0.58% |
| Srikar Dronamraju | 650 | 1.48% | 23 | 1.92% |
| Morten Rasmussen | 647 | 1.47% | 13 | 1.08% |
| Qais Yousef | 607 | 1.38% | 17 | 1.42% |
| Valentin Schneider | 596 | 1.36% | 20 | 1.67% |
| Quentin Perret | 536 | 1.22% | 7 | 0.58% |
| Tim Chen | 508 | 1.16% | 6 | 0.50% |
| Yuyang Du | 410 | 0.93% | 11 | 0.92% |
| Patrick Bellasi | 405 | 0.92% | 8 | 0.67% |
| Ricardo Neri | 363 | 0.83% | 11 | 0.92% |
| Viresh Kumar | 344 | 0.78% | 16 | 1.33% |
| Joel A Fernandes | 340 | 0.77% | 2 | 0.17% |
| Kirill V Tkhai | 335 | 0.76% | 11 | 0.92% |
| Srivatsa Vaddagiri | 315 | 0.72% | 14 | 1.17% |
| Jann Horn | 311 | 0.71% | 2 | 0.17% |
| Dietmar Eggemann | 284 | 0.65% | 15 | 1.25% |
| Chen Yu | 269 | 0.61% | 2 | 0.17% |
| Phil Auld | 263 | 0.60% | 5 | 0.42% |
| JoonSoo Kim | 248 | 0.57% | 9 | 0.75% |
| Ben Segall | 243 | 0.55% | 7 | 0.58% |
| Byungchul Park | 236 | 0.54% | 6 | 0.50% |
| Jason Low | 224 | 0.51% | 6 | 0.50% |
| Chengming Zhou | 202 | 0.46% | 11 | 0.92% |
| Mike Galbraith | 180 | 0.41% | 20 | 1.67% |
| Raghavendra K T | 172 | 0.39% | 4 | 0.33% |
| Josh Poimboeuf | 166 | 0.38% | 4 | 0.33% |
| Barry Song | 164 | 0.37% | 4 | 0.33% |
| Yun Wu | 158 | 0.36% | 4 | 0.33% |
| Brendan Jackman | 157 | 0.36% | 3 | 0.25% |
| Venkatesh Pallipadi | 131 | 0.30% | 3 | 0.25% |
| Huaixin Chang | 124 | 0.28% | 4 | 0.33% |
| Vladimir Davydov | 121 | 0.28% | 4 | 0.33% |
| Suresh B. Siddha | 121 | 0.28% | 10 | 0.83% |
| Yafang Shao | 116 | 0.26% | 2 | 0.17% |
| Linus Torvalds (pre-git) | 115 | 0.26% | 11 | 0.92% |
| Aubrey Li | 111 | 0.25% | 3 | 0.25% |
| Iulia Manda | 111 | 0.25% | 1 | 0.08% |
| Xuewen Yan | 99 | 0.23% | 2 | 0.17% |
| Vineeth Pillai | 98 | 0.22% | 1 | 0.08% |
| Thara Gopinath | 96 | 0.22% | 3 | 0.25% |
| Peter Williams | 88 | 0.20% | 5 | 0.42% |
| Frédéric Weisbecker | 86 | 0.20% | 8 | 0.67% |
| Paul Gortmaker | 84 | 0.19% | 1 | 0.08% |
| Pierre Gondois | 81 | 0.18% | 3 | 0.25% |
| Hao Jia | 79 | 0.18% | 5 | 0.42% |
| Odin Ugedal | 76 | 0.17% | 5 | 0.42% |
| Yue haibing | 75 | 0.17% | 3 | 0.25% |
| Christian Ehrhardt | 72 | 0.16% | 3 | 0.25% |
| Peng Wang | 69 | 0.16% | 3 | 0.25% |
| Michael Neuling | 66 | 0.15% | 1 | 0.08% |
| Steven Rostedt | 65 | 0.15% | 3 | 0.25% |
| Shrikanth Hegde | 64 | 0.15% | 2 | 0.17% |
| Konstantin Khlebnikov | 63 | 0.14% | 3 | 0.25% |
| Bing Huang | 59 | 0.13% | 1 | 0.08% |
| Zhen Ni | 57 | 0.13% | 2 | 0.17% |
| Thomas Gleixner | 57 | 0.13% | 4 | 0.33% |
| K Prateek Nayak | 55 | 0.13% | 1 | 0.08% |
| Christoph Hellwig | 53 | 0.12% | 2 | 0.17% |
| Clement Courbet | 51 | 0.12% | 1 | 0.08% |
| Alex Shi | 50 | 0.11% | 5 | 0.42% |
| Nico Pitre | 47 | 0.11% | 5 | 0.42% |
| Bharata B Rao | 47 | 0.11% | 7 | 0.58% |
| Aaron Lu | 46 | 0.10% | 1 | 0.08% |
| Michael Wang | 46 | 0.10% | 5 | 0.42% |
| Yicong Yang | 45 | 0.10% | 2 | 0.17% |
| Joonwoo Park | 44 | 0.10% | 1 | 0.08% |
| Gregory Haskins | 40 | 0.09% | 2 | 0.17% |
| Daniel Lezcano | 36 | 0.08% | 6 | 0.50% |
| Tejun Heo | 32 | 0.07% | 3 | 0.25% |
| Fabio Checconi | 32 | 0.07% | 1 | 0.08% |
| Xuewei Zhang | 31 | 0.07% | 1 | 0.08% |
| Linus Torvalds | 30 | 0.07% | 4 | 0.33% |
| Nikhil P Rao | 30 | 0.07% | 2 | 0.17% |
| Kefeng Wang | 29 | 0.07% | 4 | 0.33% |
| Uladzislau Rezki | 28 | 0.06% | 1 | 0.08% |
| Matthew Wilcox | 27 | 0.06% | 3 | 0.25% |
| Mathieu Desnoyers | 27 | 0.06% | 3 | 0.25% |
| Liam R. Howlett | 26 | 0.06% | 1 | 0.08% |
| Chris Redpath | 24 | 0.05% | 1 | 0.08% |
| Oleg Nesterov | 23 | 0.05% | 3 | 0.25% |
| Peter Oskolkov | 23 | 0.05% | 2 | 0.17% |
| Peter Puhov | 23 | 0.05% | 1 | 0.08% |
| Stanislaw Gruszka | 22 | 0.05% | 1 | 0.08% |
| Arjan van de Ven | 22 | 0.05% | 2 | 0.17% |
| kuyo chang | 21 | 0.05% | 1 | 0.08% |
| Rafael J. Wysocki | 21 | 0.05% | 3 | 0.25% |
| Matt Fleming | 20 | 0.05% | 2 | 0.17% |
| Davidlohr Bueso A | 19 | 0.04% | 1 | 0.08% |
| Dhaval Giani | 19 | 0.04% | 3 | 0.25% |
| Xie XiuQi | 19 | 0.04% | 1 | 0.08% |
| Jiri Slaby | 16 | 0.04% | 1 | 0.08% |
| Prashanth Nageshappa | 16 | 0.04% | 2 | 0.17% |
| zgpeng | 16 | 0.04% | 1 | 0.08% |
| Jiang Biao | 16 | 0.04% | 1 | 0.08% |
| Liangyan | 16 | 0.04% | 1 | 0.08% |
| Jeffrey Hugo | 16 | 0.04% | 1 | 0.08% |
| Wanpeng Li | 14 | 0.03% | 3 | 0.25% |
| Eric Dumazet | 14 | 0.03% | 2 | 0.17% |
| Darren Hart | 14 | 0.03% | 1 | 0.08% |
| jun qian | 14 | 0.03% | 1 | 0.08% |
| Zhang Qiao | 14 | 0.03% | 2 | 0.17% |
| Hillf Danton | 13 | 0.03% | 1 | 0.08% |
| Yuan ZhaoXiong | 13 | 0.03% | 1 | 0.08% |
| Waiman Long | 13 | 0.03% | 2 | 0.17% |
| Daisuke Nishimura | 13 | 0.03% | 1 | 0.08% |
| Daniel Axtens | 13 | 0.03% | 1 | 0.08% |
| Honglei Wang | 12 | 0.03% | 1 | 0.08% |
| Hui Su | 12 | 0.03% | 1 | 0.08% |
| Sebastian Andrzej Siewior | 12 | 0.03% | 1 | 0.08% |
| Nicholas Piggin | 12 | 0.03% | 2 | 0.17% |
| Juri Lelli | 12 | 0.03% | 3 | 0.25% |
| Art Haas | 12 | 0.03% | 1 | 0.08% |
| Tetsuo Handa | 11 | 0.03% | 1 | 0.08% |
| Michal Koutný | 11 | 0.03% | 1 | 0.08% |
| Lingutla Chandrasekhar | 11 | 0.03% | 1 | 0.08% |
| Lukasz Luba | 11 | 0.03% | 3 | 0.25% |
| Julia Lawall | 10 | 0.02% | 1 | 0.08% |
| Dmitry Adamushko | 10 | 0.02% | 2 | 0.17% |
| Steve Muckle | 10 | 0.02% | 1 | 0.08% |
| Anna-Maria Gleixner | 10 | 0.02% | 1 | 0.08% |
| Peter Boonstoppel | 9 | 0.02% | 1 | 0.08% |
| Cheng Jian | 9 | 0.02% | 1 | 0.08% |
| Ting Yang | 9 | 0.02% | 1 | 0.08% |
| Anshuman Khandual | 9 | 0.02% | 2 | 0.17% |
| Gautham R. Shenoy | 8 | 0.02% | 4 | 0.33% |
| Zhu Yanhai | 8 | 0.02% | 1 | 0.08% |
| Keisuke Nishimura | 8 | 0.02% | 1 | 0.08% |
| Tao Zhou | 8 | 0.02% | 2 | 0.17% |
| Eric W. Biedermann | 8 | 0.02% | 3 | 0.25% |
| Preeti U. Murthy | 8 | 0.02% | 2 | 0.17% |
| Mathias Krause | 8 | 0.02% | 1 | 0.08% |
| Jan Beulich | 8 | 0.02% | 2 | 0.17% |
| Naoya Horiguchi | 7 | 0.02% | 1 | 0.08% |
| Peng Liu | 7 | 0.02% | 1 | 0.08% |
| Rohit Jain | 7 | 0.02% | 1 | 0.08% |
| Kees Cook | 6 | 0.01% | 1 | 0.08% |
| Lucas De Marchi | 6 | 0.01% | 1 | 0.08% |
| Paul E. McKenney | 6 | 0.01% | 2 | 0.17% |
| Ollie Wild | 6 | 0.01% | 1 | 0.08% |
| Christoph Lameter | 6 | 0.01% | 3 | 0.25% |
| Diwakar Tundlam | 6 | 0.01% | 1 | 0.08% |
| Elena Reshetova | 6 | 0.01% | 1 | 0.08% |
| Li Zefan | 6 | 0.01% | 2 | 0.17% |
| Vlastimil Babka | 5 | 0.01% | 1 | 0.08% |
| Jens Axboe | 5 | 0.01% | 2 | 0.17% |
| Lin Ming | 5 | 0.01% | 2 | 0.17% |
| Nicholas Mc Guire | 5 | 0.01% | 1 | 0.08% |
| Rusty Russell | 5 | 0.01% | 2 | 0.17% |
| Randy Dunlap | 5 | 0.01% | 4 | 0.33% |
| Mike Travis | 5 | 0.01% | 1 | 0.08% |
| Kamezawa Hiroyuki | 4 | 0.01% | 1 | 0.08% |
| Harvey Harrison | 4 | 0.01% | 1 | 0.08% |
| Song Muchun | 4 | 0.01% | 4 | 0.33% |
| Andrew Morton | 4 | 0.01% | 3 | 0.25% |
| Andrey Vagin | 4 | 0.01% | 1 | 0.08% |
| Balbir Singh | 4 | 0.01% | 1 | 0.08% |
| Andrei Epure | 4 | 0.01% | 1 | 0.08% |
| Hugh Dickins | 4 | 0.01% | 1 | 0.08% |
| Hideaki Yoshifuji / 吉藤英明 | 4 | 0.01% | 1 | 0.08% |
| Leo Yan | 3 | 0.01% | 2 | 0.17% |
| Tom Rix | 3 | 0.01% | 1 | 0.08% |
| Aneesh Kumar K.V | 3 | 0.01% | 1 | 0.08% |
| Xunlei Pang | 3 | 0.01% | 3 | 0.25% |
| Uros Bizjak | 3 | 0.01% | 1 | 0.08% |
| Al Viro | 3 | 0.01% | 2 | 0.17% |
| Alexei Starovoitov | 3 | 0.01% | 1 | 0.08% |
| Masahiro Yamada | 3 | 0.01% | 1 | 0.08% |
| Phil Carmody | 3 | 0.01% | 1 | 0.08% |
| Steven Cole | 2 | 0.00% | 1 | 0.08% |
| Kamalesh Babulal | 2 | 0.00% | 1 | 0.08% |
| Norbert Manthey | 2 | 0.00% | 1 | 0.08% |
| Michel Lespinasse | 2 | 0.00% | 1 | 0.08% |
| Kazuto Miyoshi | 2 | 0.00% | 1 | 0.08% |
| Yury Norov | 2 | 0.00% | 1 | 0.08% |
| Libo Chen | 2 | 0.00% | 1 | 0.08% |
| Josef Bacik | 2 | 0.00% | 1 | 0.08% |
| Emese Revfy | 1 | 0.00% | 1 | 0.08% |
| Greg Kroah-Hartman | 1 | 0.00% | 1 | 0.08% |
| Yi Wang | 1 | 0.00% | 1 | 0.08% |
| Yong Zhang | 1 | 0.00% | 1 | 0.08% |
| Frank Mayhar | 1 | 0.00% | 1 | 0.08% |
| Vaidyanathan Srinivasan | 1 | 0.00% | 1 | 0.08% |
| Qian Cai | 1 | 0.00% | 1 | 0.08% |
| Ramkumar Ramachandra | 1 | 0.00% | 1 | 0.08% |
| H Hartley Sweeten | 1 | 0.00% | 1 | 0.08% |
| Andreea-Cristina Bernat | 1 | 0.00% | 1 | 0.08% |
| M.Baris Demiray | 1 | 0.00% | 1 | 0.08% |
| Zhihui Zhang | 1 | 0.00% | 1 | 0.08% |
| Gustavo A. R. Silva | 1 | 0.00% | 1 | 0.08% |
| Xianting Tian | 1 | 0.00% | 1 | 0.08% |
| Christian Engelmayer | 1 | 0.00% | 1 | 0.08% |
| Arnd Bergmann | 1 | 0.00% | 1 | 0.08% |
| Luca Abeni | 1 | 0.00% | 1 | 0.08% |
| Yacine Belkadi | 1 | 0.00% | 1 | 0.08% |
| Total | 43892 | 1201 |
// SPDX-License-Identifier: GPL-2.0 /* * Completely Fair Scheduling (CFS) Class (SCHED_NORMAL/SCHED_BATCH) * * Copyright (C) 2007 Red Hat, Inc., Ingo Molnar <mingo@redhat.com> * * Interactivity improvements by Mike Galbraith * (C) 2007 Mike Galbraith <efault@gmx.de> * * Various enhancements by Dmitry Adamushko. * (C) 2007 Dmitry Adamushko <dmitry.adamushko@gmail.com> * * Group scheduling enhancements by Srivatsa Vaddagiri * Copyright IBM Corporation, 2007 * Author: Srivatsa Vaddagiri <vatsa@linux.vnet.ibm.com> * * Scaled math optimizations by Thomas Gleixner * Copyright (C) 2007, Thomas Gleixner <tglx@linutronix.de> * * Adaptive scheduling granularity, math enhancements by Peter Zijlstra * Copyright (C) 2007 Red Hat, Inc., Peter Zijlstra */ #include <linux/energy_model.h> #include <linux/mmap_lock.h> #include <linux/hugetlb_inline.h> #include <linux/jiffies.h> #include <linux/mm_api.h> #include <linux/highmem.h> #include <linux/spinlock_api.h> #include <linux/cpumask_api.h> #include <linux/lockdep_api.h> #include <linux/softirq.h> #include <linux/refcount_api.h> #include <linux/topology.h> #include <linux/sched/clock.h> #include <linux/sched/cond_resched.h> #include <linux/sched/cputime.h> #include <linux/sched/isolation.h> #include <linux/sched/nohz.h> #include <linux/cpuidle.h> #include <linux/interrupt.h> #include <linux/memory-tiers.h> #include <linux/mempolicy.h> #include <linux/mutex_api.h> #include <linux/profile.h> #include <linux/psi.h> #include <linux/ratelimit.h> #include <linux/task_work.h> #include <linux/rbtree_augmented.h> #include <asm/switch_to.h> #include "sched.h" #include "stats.h" #include "autogroup.h" /* * The initial- and re-scaling of tunables is configurable * * Options are: * * SCHED_TUNABLESCALING_NONE - unscaled, always *1 * SCHED_TUNABLESCALING_LOG - scaled logarithmical, *1+ilog(ncpus) * SCHED_TUNABLESCALING_LINEAR - scaled linear, *ncpus * * (default SCHED_TUNABLESCALING_LOG = *(1+ilog(ncpus)) */ unsigned int sysctl_sched_tunable_scaling = SCHED_TUNABLESCALING_LOG; /* * Minimal preemption granularity for CPU-bound tasks: * * (default: 0.75 msec * (1 + ilog(ncpus)), units: nanoseconds) */ unsigned int sysctl_sched_base_slice = 750000ULL; static unsigned int normalized_sysctl_sched_base_slice = 750000ULL; const_debug unsigned int sysctl_sched_migration_cost = 500000UL; int sched_thermal_decay_shift; static int __init setup_sched_thermal_decay_shift(char *str) { int _shift = 0; if (kstrtoint(str, 0, &_shift)) pr_warn("Unable to set scheduler thermal pressure decay shift parameter\n"); sched_thermal_decay_shift = clamp(_shift, 0, 10); return 1; } __setup("sched_thermal_decay_shift=", setup_sched_thermal_decay_shift); #ifdef CONFIG_SMP /* * For asym packing, by default the lower numbered CPU has higher priority. */ int __weak arch_asym_cpu_priority(int cpu) { return -cpu; } /* * The margin used when comparing utilization with CPU capacity. * * (default: ~20%) */ #define fits_capacity(cap, max) ((cap) * 1280 < (max) * 1024) /* * The margin used when comparing CPU capacities. * is 'cap1' noticeably greater than 'cap2' * * (default: ~5%) */ #define capacity_greater(cap1, cap2) ((cap1) * 1024 > (cap2) * 1078) #endif #ifdef CONFIG_CFS_BANDWIDTH /* * Amount of runtime to allocate from global (tg) to local (per-cfs_rq) pool * each time a cfs_rq requests quota. * * Note: in the case that the slice exceeds the runtime remaining (either due * to consumption or the quota being specified to be smaller than the slice) * we will always only issue the remaining available time. * * (default: 5 msec, units: microseconds) */ static unsigned int sysctl_sched_cfs_bandwidth_slice = 5000UL; #endif #ifdef CONFIG_NUMA_BALANCING /* Restrict the NUMA promotion throughput (MB/s) for each target node. */ static unsigned int sysctl_numa_balancing_promote_rate_limit = 65536; #endif #ifdef CONFIG_SYSCTL static struct ctl_table sched_fair_sysctls[] = { #ifdef CONFIG_CFS_BANDWIDTH { .procname = "sched_cfs_bandwidth_slice_us", .data = &sysctl_sched_cfs_bandwidth_slice, .maxlen = sizeof(unsigned int), .mode = 0644, .proc_handler = proc_dointvec_minmax, .extra1 = SYSCTL_ONE, }, #endif #ifdef CONFIG_NUMA_BALANCING { .procname = "numa_balancing_promote_rate_limit_MBps", .data = &sysctl_numa_balancing_promote_rate_limit, .maxlen = sizeof(unsigned int), .mode = 0644, .proc_handler = proc_dointvec_minmax, .extra1 = SYSCTL_ZERO, }, #endif /* CONFIG_NUMA_BALANCING */ {} }; static int __init sched_fair_sysctl_init(void) { register_sysctl_init("kernel", sched_fair_sysctls); return 0; } late_initcall(sched_fair_sysctl_init); #endif static inline void update_load_add(struct load_weight *lw, unsigned long inc) { lw->weight += inc; lw->inv_weight = 0; } static inline void update_load_sub(struct load_weight *lw, unsigned long dec) { lw->weight -= dec; lw->inv_weight = 0; } static inline void update_load_set(struct load_weight *lw, unsigned long w) { lw->weight = w; lw->inv_weight = 0; } /* * Increase the granularity value when there are more CPUs, * because with more CPUs the 'effective latency' as visible * to users decreases. But the relationship is not linear, * so pick a second-best guess by going with the log2 of the * number of CPUs. * * This idea comes from the SD scheduler of Con Kolivas: */ static unsigned int get_update_sysctl_factor(void) { unsigned int cpus = min_t(unsigned int, num_online_cpus(), 8); unsigned int factor; switch (sysctl_sched_tunable_scaling) { case SCHED_TUNABLESCALING_NONE: factor = 1; break; case SCHED_TUNABLESCALING_LINEAR: factor = cpus; break; case SCHED_TUNABLESCALING_LOG: default: factor = 1 + ilog2(cpus); break; } return factor; } static void update_sysctl(void) { unsigned int factor = get_update_sysctl_factor(); #define SET_SYSCTL(name) \ (sysctl_##name = (factor) * normalized_sysctl_##name) SET_SYSCTL(sched_base_slice); #undef SET_SYSCTL } void __init sched_init_granularity(void) { update_sysctl(); } #define WMULT_CONST (~0U) #define WMULT_SHIFT 32 static void __update_inv_weight(struct load_weight *lw) { unsigned long w; if (likely(lw->inv_weight)) return; w = scale_load_down(lw->weight); if (BITS_PER_LONG > 32 && unlikely(w >= WMULT_CONST)) lw->inv_weight = 1; else if (unlikely(!w)) lw->inv_weight = WMULT_CONST; else lw->inv_weight = WMULT_CONST / w; } /* * delta_exec * weight / lw.weight * OR * (delta_exec * (weight * lw->inv_weight)) >> WMULT_SHIFT * * Either weight := NICE_0_LOAD and lw \e sched_prio_to_wmult[], in which case * we're guaranteed shift stays positive because inv_weight is guaranteed to * fit 32 bits, and NICE_0_LOAD gives another 10 bits; therefore shift >= 22. * * Or, weight =< lw.weight (because lw.weight is the runqueue weight), thus * weight/lw.weight <= 1, and therefore our shift will also be positive. */ static u64 __calc_delta(u64 delta_exec, unsigned long weight, struct load_weight *lw) { u64 fact = scale_load_down(weight); u32 fact_hi = (u32)(fact >> 32); int shift = WMULT_SHIFT; int fs; __update_inv_weight(lw); if (unlikely(fact_hi)) { fs = fls(fact_hi); shift -= fs; fact >>= fs; } fact = mul_u32_u32(fact, lw->inv_weight); fact_hi = (u32)(fact >> 32); if (fact_hi) { fs = fls(fact_hi); shift -= fs; fact >>= fs; } return mul_u64_u32_shr(delta_exec, fact, shift); } /* * delta /= w */ static inline u64 calc_delta_fair(u64 delta, struct sched_entity *se) { if (unlikely(se->load.weight != NICE_0_LOAD)) delta = __calc_delta(delta, NICE_0_LOAD, &se->load); return delta; } const struct sched_class fair_sched_class; /************************************************************** * CFS operations on generic schedulable entities: */ #ifdef CONFIG_FAIR_GROUP_SCHED /* Walk up scheduling entities hierarchy */ #define for_each_sched_entity(se) \ for (; se; se = se->parent) static inline bool list_add_leaf_cfs_rq(struct cfs_rq *cfs_rq) { struct rq *rq = rq_of(cfs_rq); int cpu = cpu_of(rq); if (cfs_rq->on_list) return rq->tmp_alone_branch == &rq->leaf_cfs_rq_list; cfs_rq->on_list = 1; /* * Ensure we either appear before our parent (if already * enqueued) or force our parent to appear after us when it is * enqueued. The fact that we always enqueue bottom-up * reduces this to two cases and a special case for the root * cfs_rq. Furthermore, it also means that we will always reset * tmp_alone_branch either when the branch is connected * to a tree or when we reach the top of the tree */ if (cfs_rq->tg->parent && cfs_rq->tg->parent->cfs_rq[cpu]->on_list) { /* * If parent is already on the list, we add the child * just before. Thanks to circular linked property of * the list, this means to put the child at the tail * of the list that starts by parent. */ list_add_tail_rcu(&cfs_rq->leaf_cfs_rq_list, &(cfs_rq->tg->parent->cfs_rq[cpu]->leaf_cfs_rq_list)); /* * The branch is now connected to its tree so we can * reset tmp_alone_branch to the beginning of the * list. */ rq->tmp_alone_branch = &rq->leaf_cfs_rq_list; return true; } if (!cfs_rq->tg->parent) { /* * cfs rq without parent should be put * at the tail of the list. */ list_add_tail_rcu(&cfs_rq->leaf_cfs_rq_list, &rq->leaf_cfs_rq_list); /* * We have reach the top of a tree so we can reset * tmp_alone_branch to the beginning of the list. */ rq->tmp_alone_branch = &rq->leaf_cfs_rq_list; return true; } /* * The parent has not already been added so we want to * make sure that it will be put after us. * tmp_alone_branch points to the begin of the branch * where we will add parent. */ list_add_rcu(&cfs_rq->leaf_cfs_rq_list, rq->tmp_alone_branch); /* * update tmp_alone_branch to points to the new begin * of the branch */ rq->tmp_alone_branch = &cfs_rq->leaf_cfs_rq_list; return false; } static inline void list_del_leaf_cfs_rq(struct cfs_rq *cfs_rq) { if (cfs_rq->on_list) { struct rq *rq = rq_of(cfs_rq); /* * With cfs_rq being unthrottled/throttled during an enqueue, * it can happen the tmp_alone_branch points the a leaf that * we finally want to del. In this case, tmp_alone_branch moves * to the prev element but it will point to rq->leaf_cfs_rq_list * at the end of the enqueue. */ if (rq->tmp_alone_branch == &cfs_rq->leaf_cfs_rq_list) rq->tmp_alone_branch = cfs_rq->leaf_cfs_rq_list.prev; list_del_rcu(&cfs_rq->leaf_cfs_rq_list); cfs_rq->on_list = 0; } } static inline void assert_list_leaf_cfs_rq(struct rq *rq) { SCHED_WARN_ON(rq->tmp_alone_branch != &rq->leaf_cfs_rq_list); } /* Iterate thr' all leaf cfs_rq's on a runqueue */ #define for_each_leaf_cfs_rq_safe(rq, cfs_rq, pos) \ list_for_each_entry_safe(cfs_rq, pos, &rq->leaf_cfs_rq_list, \ leaf_cfs_rq_list) /* Do the two (enqueued) entities belong to the same group ? */ static inline struct cfs_rq * is_same_group(struct sched_entity *se, struct sched_entity *pse) { if (se->cfs_rq == pse->cfs_rq) return se->cfs_rq; return NULL; } static inline struct sched_entity *parent_entity(const struct sched_entity *se) { return se->parent; } static void find_matching_se(struct sched_entity **se, struct sched_entity **pse) { int se_depth, pse_depth; /* * preemption test can be made between sibling entities who are in the * same cfs_rq i.e who have a common parent. Walk up the hierarchy of * both tasks until we find their ancestors who are siblings of common * parent. */ /* First walk up until both entities are at same depth */ se_depth = (*se)->depth; pse_depth = (*pse)->depth; while (se_depth > pse_depth) { se_depth--; *se = parent_entity(*se); } while (pse_depth > se_depth) { pse_depth--; *pse = parent_entity(*pse); } while (!is_same_group(*se, *pse)) { *se = parent_entity(*se); *pse = parent_entity(*pse); } } static int tg_is_idle(struct task_group *tg) { return tg->idle > 0; } static int cfs_rq_is_idle(struct cfs_rq *cfs_rq) { return cfs_rq->idle > 0; } static int se_is_idle(struct sched_entity *se) { if (entity_is_task(se)) return task_has_idle_policy(task_of(se)); return cfs_rq_is_idle(group_cfs_rq(se)); } #else /* !CONFIG_FAIR_GROUP_SCHED */ #define for_each_sched_entity(se) \ for (; se; se = NULL) static inline bool list_add_leaf_cfs_rq(struct cfs_rq *cfs_rq) { return true; } static inline void list_del_leaf_cfs_rq(struct cfs_rq *cfs_rq) { } static inline void assert_list_leaf_cfs_rq(struct rq *rq) { } #define for_each_leaf_cfs_rq_safe(rq, cfs_rq, pos) \ for (cfs_rq = &rq->cfs, pos = NULL; cfs_rq; cfs_rq = pos) static inline struct sched_entity *parent_entity(struct sched_entity *se) { return NULL; } static inline void find_matching_se(struct sched_entity **se, struct sched_entity **pse) { } static inline int tg_is_idle(struct task_group *tg) { return 0; } static int cfs_rq_is_idle(struct cfs_rq *cfs_rq) { return 0; } static int se_is_idle(struct sched_entity *se) { return 0; } #endif /* CONFIG_FAIR_GROUP_SCHED */ static __always_inline void account_cfs_rq_runtime(struct cfs_rq *cfs_rq, u64 delta_exec); /************************************************************** * Scheduling class tree data structure manipulation methods: */ static inline u64 max_vruntime(u64 max_vruntime, u64 vruntime) { s64 delta = (s64)(vruntime - max_vruntime); if (delta > 0) max_vruntime = vruntime; return max_vruntime; } static inline u64 min_vruntime(u64 min_vruntime, u64 vruntime) { s64 delta = (s64)(vruntime - min_vruntime); if (delta < 0) min_vruntime = vruntime; return min_vruntime; } static inline bool entity_before(const struct sched_entity *a, const struct sched_entity *b) { return (s64)(a->vruntime - b->vruntime) < 0; } static inline s64 entity_key(struct cfs_rq *cfs_rq, struct sched_entity *se) { return (s64)(se->vruntime - cfs_rq->min_vruntime); } #define __node_2_se(node) \ rb_entry((node), struct sched_entity, run_node) /* * Compute virtual time from the per-task service numbers: * * Fair schedulers conserve lag: * * \Sum lag_i = 0 * * Where lag_i is given by: * * lag_i = S - s_i = w_i * (V - v_i) * * Where S is the ideal service time and V is it's virtual time counterpart. * Therefore: * * \Sum lag_i = 0 * \Sum w_i * (V - v_i) = 0 * \Sum w_i * V - w_i * v_i = 0 * * From which we can solve an expression for V in v_i (which we have in * se->vruntime): * * \Sum v_i * w_i \Sum v_i * w_i * V = -------------- = -------------- * \Sum w_i W * * Specifically, this is the weighted average of all entity virtual runtimes. * * [[ NOTE: this is only equal to the ideal scheduler under the condition * that join/leave operations happen at lag_i = 0, otherwise the * virtual time has non-continguous motion equivalent to: * * V +-= lag_i / W * * Also see the comment in place_entity() that deals with this. ]] * * However, since v_i is u64, and the multiplcation could easily overflow * transform it into a relative form that uses smaller quantities: * * Substitute: v_i == (v_i - v0) + v0 * * \Sum ((v_i - v0) + v0) * w_i \Sum (v_i - v0) * w_i * V = ---------------------------- = --------------------- + v0 * W W * * Which we track using: * * v0 := cfs_rq->min_vruntime * \Sum (v_i - v0) * w_i := cfs_rq->avg_vruntime * \Sum w_i := cfs_rq->avg_load * * Since min_vruntime is a monotonic increasing variable that closely tracks * the per-task service, these deltas: (v_i - v), will be in the order of the * maximal (virtual) lag induced in the system due to quantisation. * * Also, we use scale_load_down() to reduce the size. * * As measured, the max (key * weight) value was ~44 bits for a kernel build. */ static void avg_vruntime_add(struct cfs_rq *cfs_rq, struct sched_entity *se) { unsigned long weight = scale_load_down(se->load.weight); s64 key = entity_key(cfs_rq, se); cfs_rq->avg_vruntime += key * weight; cfs_rq->avg_load += weight; } static void avg_vruntime_sub(struct cfs_rq *cfs_rq, struct sched_entity *se) { unsigned long weight = scale_load_down(se->load.weight); s64 key = entity_key(cfs_rq, se); cfs_rq->avg_vruntime -= key * weight; cfs_rq->avg_load -= weight; } static inline void avg_vruntime_update(struct cfs_rq *cfs_rq, s64 delta) { /* * v' = v + d ==> avg_vruntime' = avg_runtime - d*avg_load */ cfs_rq->avg_vruntime -= cfs_rq->avg_load * delta; } /* * Specifically: avg_runtime() + 0 must result in entity_eligible() := true * For this to be so, the result of this function must have a left bias. */ u64 avg_vruntime(struct cfs_rq *cfs_rq) { struct sched_entity *curr = cfs_rq->curr; s64 avg = cfs_rq->avg_vruntime; long load = cfs_rq->avg_load; if (curr && curr->on_rq) { unsigned long weight = scale_load_down(curr->load.weight); avg += entity_key(cfs_rq, curr) * weight; load += weight; } if (load) { /* sign flips effective floor / ceil */ if (avg < 0) avg -= (load - 1); avg = div_s64(avg, load); } return cfs_rq->min_vruntime + avg; } /* * lag_i = S - s_i = w_i * (V - v_i) * * However, since V is approximated by the weighted average of all entities it * is possible -- by addition/removal/reweight to the tree -- to move V around * and end up with a larger lag than we started with. * * Limit this to either double the slice length with a minimum of TICK_NSEC * since that is the timing granularity. * * EEVDF gives the following limit for a steady state system: * * -r_max < lag < max(r_max, q) * * XXX could add max_slice to the augmented data to track this. */ static void update_entity_lag(struct cfs_rq *cfs_rq, struct sched_entity *se) { s64 lag, limit; SCHED_WARN_ON(!se->on_rq); lag = avg_vruntime(cfs_rq) - se->vruntime; limit = calc_delta_fair(max_t(u64, 2*se->slice, TICK_NSEC), se); se->vlag = clamp(lag, -limit, limit); } /* * Entity is eligible once it received less service than it ought to have, * eg. lag >= 0. * * lag_i = S - s_i = w_i*(V - v_i) * * lag_i >= 0 -> V >= v_i * * \Sum (v_i - v)*w_i * V = ------------------ + v * \Sum w_i * * lag_i >= 0 -> \Sum (v_i - v)*w_i >= (v_i - v)*(\Sum w_i) * * Note: using 'avg_vruntime() > se->vruntime' is inacurate due * to the loss in precision caused by the division. */ int entity_eligible(struct cfs_rq *cfs_rq, struct sched_entity *se) { struct sched_entity *curr = cfs_rq->curr; s64 avg = cfs_rq->avg_vruntime; long load = cfs_rq->avg_load; if (curr && curr->on_rq) { unsigned long weight = scale_load_down(curr->load.weight); avg += entity_key(cfs_rq, curr) * weight; load += weight; } return avg >= entity_key(cfs_rq, se) * load; } static u64 __update_min_vruntime(struct cfs_rq *cfs_rq, u64 vruntime) { u64 min_vruntime = cfs_rq->min_vruntime; /* * open coded max_vruntime() to allow updating avg_vruntime */ s64 delta = (s64)(vruntime - min_vruntime); if (delta > 0) { avg_vruntime_update(cfs_rq, delta); min_vruntime = vruntime; } return min_vruntime; } static void update_min_vruntime(struct cfs_rq *cfs_rq) { struct sched_entity *se = __pick_first_entity(cfs_rq); struct sched_entity *curr = cfs_rq->curr; u64 vruntime = cfs_rq->min_vruntime; if (curr) { if (curr->on_rq) vruntime = curr->vruntime; else curr = NULL; } if (se) { if (!curr) vruntime = se->vruntime; else vruntime = min_vruntime(vruntime, se->vruntime); } /* ensure we never gain time by being placed backwards. */ u64_u32_store(cfs_rq->min_vruntime, __update_min_vruntime(cfs_rq, vruntime)); } static inline bool __entity_less(struct rb_node *a, const struct rb_node *b) { return entity_before(__node_2_se(a), __node_2_se(b)); } #define deadline_gt(field, lse, rse) ({ (s64)((lse)->field - (rse)->field) > 0; }) static inline void __update_min_deadline(struct sched_entity *se, struct rb_node *node) { if (node) { struct sched_entity *rse = __node_2_se(node); if (deadline_gt(min_deadline, se, rse)) se->min_deadline = rse->min_deadline; } } /* * se->min_deadline = min(se->deadline, left->min_deadline, right->min_deadline) */ static inline bool min_deadline_update(struct sched_entity *se, bool exit) { u64 old_min_deadline = se->min_deadline; struct rb_node *node = &se->run_node; se->min_deadline = se->deadline; __update_min_deadline(se, node->rb_right); __update_min_deadline(se, node->rb_left); return se->min_deadline == old_min_deadline; } RB_DECLARE_CALLBACKS(static, min_deadline_cb, struct sched_entity, run_node, min_deadline, min_deadline_update); /* * Enqueue an entity into the rb-tree: */ static void __enqueue_entity(struct cfs_rq *cfs_rq, struct sched_entity *se) { avg_vruntime_add(cfs_rq, se); se->min_deadline = se->deadline; rb_add_augmented_cached(&se->run_node, &cfs_rq->tasks_timeline, __entity_less, &min_deadline_cb); } static void __dequeue_entity(struct cfs_rq *cfs_rq, struct sched_entity *se) { rb_erase_augmented_cached(&se->run_node, &cfs_rq->tasks_timeline, &min_deadline_cb); avg_vruntime_sub(cfs_rq, se); } struct sched_entity *__pick_first_entity(struct cfs_rq *cfs_rq) { struct rb_node *left = rb_first_cached(&cfs_rq->tasks_timeline); if (!left) return NULL; return __node_2_se(left); } /* * Earliest Eligible Virtual Deadline First * * In order to provide latency guarantees for different request sizes * EEVDF selects the best runnable task from two criteria: * * 1) the task must be eligible (must be owed service) * * 2) from those tasks that meet 1), we select the one * with the earliest virtual deadline. * * We can do this in O(log n) time due to an augmented RB-tree. The * tree keeps the entries sorted on service, but also functions as a * heap based on the deadline by keeping: * * se->min_deadline = min(se->deadline, se->{left,right}->min_deadline) * * Which allows an EDF like search on (sub)trees. */ static struct sched_entity *__pick_eevdf(struct cfs_rq *cfs_rq) { struct rb_node *node = cfs_rq->tasks_timeline.rb_root.rb_node; struct sched_entity *curr = cfs_rq->curr; struct sched_entity *best = NULL; struct sched_entity *best_left = NULL; if (curr && (!curr->on_rq || !entity_eligible(cfs_rq, curr))) curr = NULL; best = curr; /* * Once selected, run a task until it either becomes non-eligible or * until it gets a new slice. See the HACK in set_next_entity(). */ if (sched_feat(RUN_TO_PARITY) && curr && curr->vlag == curr->deadline) return curr; while (node) { struct sched_entity *se = __node_2_se(node); /* * If this entity is not eligible, try the left subtree. */ if (!entity_eligible(cfs_rq, se)) { node = node->rb_left; continue; } /* * Now we heap search eligible trees for the best (min_)deadline */ if (!best || deadline_gt(deadline, best, se)) best = se; /* * Every se in a left branch is eligible, keep track of the * branch with the best min_deadline */ if (node->rb_left) { struct sched_entity *left = __node_2_se(node->rb_left); if (!best_left || deadline_gt(min_deadline, best_left, left)) best_left = left; /* * min_deadline is in the left branch. rb_left and all * descendants are eligible, so immediately switch to the second * loop. */ if (left->min_deadline == se->min_deadline) break; } /* min_deadline is at this node, no need to look right */ if (se->deadline == se->min_deadline) break; /* else min_deadline is in the right branch. */ node = node->rb_right; } /* * We ran into an eligible node which is itself the best. * (Or nr_running == 0 and both are NULL) */ if (!best_left || (s64)(best_left->min_deadline - best->deadline) > 0) return best; /* * Now best_left and all of its children are eligible, and we are just * looking for deadline == min_deadline */ node = &best_left->run_node; while (node) { struct sched_entity *se = __node_2_se(node); /* min_deadline is the current node */ if (se->deadline == se->min_deadline) return se; /* min_deadline is in the left branch */ if (node->rb_left && __node_2_se(node->rb_left)->min_deadline == se->min_deadline) { node = node->rb_left; continue; } /* else min_deadline is in the right branch */ node = node->rb_right; } return NULL; } static struct sched_entity *pick_eevdf(struct cfs_rq *cfs_rq) { struct sched_entity *se = __pick_eevdf(cfs_rq); if (!se) { struct sched_entity *left = __pick_first_entity(cfs_rq); if (left) { pr_err("EEVDF scheduling fail, picking leftmost\n"); return left; } } return se; } #ifdef CONFIG_SCHED_DEBUG struct sched_entity *__pick_last_entity(struct cfs_rq *cfs_rq) { struct rb_node *last = rb_last(&cfs_rq->tasks_timeline.rb_root); if (!last) return NULL; return __node_2_se(last); } /************************************************************** * Scheduling class statistics methods: */ #ifdef CONFIG_SMP int sched_update_scaling(void) { unsigned int factor = get_update_sysctl_factor(); #define WRT_SYSCTL(name) \ (normalized_sysctl_##name = sysctl_##name / (factor)) WRT_SYSCTL(sched_base_slice); #undef WRT_SYSCTL return 0; } #endif #endif static void clear_buddies(struct cfs_rq *cfs_rq, struct sched_entity *se); /* * XXX: strictly: vd_i += N*r_i/w_i such that: vd_i > ve_i * this is probably good enough. */ static void update_deadline(struct cfs_rq *cfs_rq, struct sched_entity *se) { if ((s64)(se->vruntime - se->deadline) < 0) return; /* * For EEVDF the virtual time slope is determined by w_i (iow. * nice) while the request time r_i is determined by * sysctl_sched_base_slice. */ se->slice = sysctl_sched_base_slice; /* * EEVDF: vd_i = ve_i + r_i / w_i */ se->deadline = se->vruntime + calc_delta_fair(se->slice, se); /* * The task has consumed its request, reschedule. */ if (cfs_rq->nr_running > 1) { resched_curr(rq_of(cfs_rq)); clear_buddies(cfs_rq, se); } } #include "pelt.h" #ifdef CONFIG_SMP static int select_idle_sibling(struct task_struct *p, int prev_cpu, int cpu); static unsigned long task_h_load(struct task_struct *p); static unsigned long capacity_of(int cpu); /* Give new sched_entity start runnable values to heavy its load in infant time */ void init_entity_runnable_average(struct sched_entity *se) { struct sched_avg *sa = &se->avg; memset(sa, 0, sizeof(*sa)); /* * Tasks are initialized with full load to be seen as heavy tasks until * they get a chance to stabilize to their real load level. * Group entities are initialized with zero load to reflect the fact that * nothing has been attached to the task group yet. */ if (entity_is_task(se)) sa->load_avg = scale_load_down(se->load.weight); /* when this task enqueue'ed, it will contribute to its cfs_rq's load_avg */ } /* * With new tasks being created, their initial util_avgs are extrapolated * based on the cfs_rq's current util_avg: * * util_avg = cfs_rq->util_avg / (cfs_rq->load_avg + 1) * se.load.weight * * However, in many cases, the above util_avg does not give a desired * value. Moreover, the sum of the util_avgs may be divergent, such * as when the series is a harmonic series. * * To solve this problem, we also cap the util_avg of successive tasks to * only 1/2 of the left utilization budget: * * util_avg_cap = (cpu_scale - cfs_rq->avg.util_avg) / 2^n * * where n denotes the nth task and cpu_scale the CPU capacity. * * For example, for a CPU with 1024 of capacity, a simplest series from * the beginning would be like: * * task util_avg: 512, 256, 128, 64, 32, 16, 8, ... * cfs_rq util_avg: 512, 768, 896, 960, 992, 1008, 1016, ... * * Finally, that extrapolated util_avg is clamped to the cap (util_avg_cap) * if util_avg > util_avg_cap. */ void post_init_entity_util_avg(struct task_struct *p) { struct sched_entity *se = &p->se; struct cfs_rq *cfs_rq = cfs_rq_of(se); struct sched_avg *sa = &se->avg; long cpu_scale = arch_scale_cpu_capacity(cpu_of(rq_of(cfs_rq))); long cap = (long)(cpu_scale - cfs_rq->avg.util_avg) / 2; if (p->sched_class != &fair_sched_class) { /* * For !fair tasks do: * update_cfs_rq_load_avg(now, cfs_rq); attach_entity_load_avg(cfs_rq, se); switched_from_fair(rq, p); * * such that the next switched_to_fair() has the * expected state. */ se->avg.last_update_time = cfs_rq_clock_pelt(cfs_rq); return; } if (cap > 0) { if (cfs_rq->avg.util_avg != 0) { sa->util_avg = cfs_rq->avg.util_avg * se->load.weight; sa->util_avg /= (cfs_rq->avg.load_avg + 1); if (sa->util_avg > cap) sa->util_avg = cap; } else { sa->util_avg = cap; } } sa->runnable_avg = sa->util_avg; } #else /* !CONFIG_SMP */ void init_entity_runnable_average(struct sched_entity *se) { } void post_init_entity_util_avg(struct task_struct *p) { } static void update_tg_load_avg(struct cfs_rq *cfs_rq) { } #endif /* CONFIG_SMP */ /* * Update the current task's runtime statistics. */ static void update_curr(struct cfs_rq *cfs_rq) { struct sched_entity *curr = cfs_rq->curr; u64 now = rq_clock_task(rq_of(cfs_rq)); u64 delta_exec; if (unlikely(!curr)) return; delta_exec = now - curr->exec_start; if (unlikely((s64)delta_exec <= 0)) return; curr->exec_start = now; if (schedstat_enabled()) { struct sched_statistics *stats; stats = __schedstats_from_se(curr); __schedstat_set(stats->exec_max, max(delta_exec, stats->exec_max)); } curr->sum_exec_runtime += delta_exec; schedstat_add(cfs_rq->exec_clock, delta_exec); curr->vruntime += calc_delta_fair(delta_exec, curr); update_deadline(cfs_rq, curr); update_min_vruntime(cfs_rq); if (entity_is_task(curr)) { struct task_struct *curtask = task_of(curr); trace_sched_stat_runtime(curtask, delta_exec, curr->vruntime); cgroup_account_cputime(curtask, delta_exec); account_group_exec_runtime(curtask, delta_exec); } account_cfs_rq_runtime(cfs_rq, delta_exec); } static void update_curr_fair(struct rq *rq) { update_curr(cfs_rq_of(&rq->curr->se)); } static inline void update_stats_wait_start_fair(struct cfs_rq *cfs_rq, struct sched_entity *se) { struct sched_statistics *stats; struct task_struct *p = NULL; if (!schedstat_enabled()) return; stats = __schedstats_from_se(se); if (entity_is_task(se)) p = task_of(se); __update_stats_wait_start(rq_of(cfs_rq), p, stats); } static inline void update_stats_wait_end_fair(struct cfs_rq *cfs_rq, struct sched_entity *se) { struct sched_statistics *stats; struct task_struct *p = NULL; if (!schedstat_enabled()) return; stats = __schedstats_from_se(se); /* * When the sched_schedstat changes from 0 to 1, some sched se * maybe already in the runqueue, the se->statistics.wait_start * will be 0.So it will let the delta wrong. We need to avoid this * scenario. */ if (unlikely(!schedstat_val(stats->wait_start))) return; if (entity_is_task(se)) p = task_of(se); __update_stats_wait_end(rq_of(cfs_rq), p, stats); } static inline void update_stats_enqueue_sleeper_fair(struct cfs_rq *cfs_rq, struct sched_entity *se) { struct sched_statistics *stats; struct task_struct *tsk = NULL; if (!schedstat_enabled()) return; stats = __schedstats_from_se(se); if (entity_is_task(se)) tsk = task_of(se); __update_stats_enqueue_sleeper(rq_of(cfs_rq), tsk, stats); } /* * Task is being enqueued - update stats: */ static inline void update_stats_enqueue_fair(struct cfs_rq *cfs_rq, struct sched_entity *se, int flags) { if (!schedstat_enabled()) return; /* * Are we enqueueing a waiting task? (for current tasks * a dequeue/enqueue event is a NOP) */ if (se != cfs_rq->curr) update_stats_wait_start_fair(cfs_rq, se); if (flags & ENQUEUE_WAKEUP) update_stats_enqueue_sleeper_fair(cfs_rq, se); } static inline void update_stats_dequeue_fair(struct cfs_rq *cfs_rq, struct sched_entity *se, int flags) { if (!schedstat_enabled()) return; /* * Mark the end of the wait period if dequeueing a * waiting task: */ if (se != cfs_rq->curr) update_stats_wait_end_fair(cfs_rq, se); if ((flags & DEQUEUE_SLEEP) && entity_is_task(se)) { struct task_struct *tsk = task_of(se); unsigned int state; /* XXX racy against TTWU */ state = READ_ONCE(tsk->__state); if (state & TASK_INTERRUPTIBLE) __schedstat_set(tsk->stats.sleep_start, rq_clock(rq_of(cfs_rq))); if (state & TASK_UNINTERRUPTIBLE) __schedstat_set(tsk->stats.block_start, rq_clock(rq_of(cfs_rq))); } } /* * We are picking a new current task - update its stats: */ static inline void update_stats_curr_start(struct cfs_rq *cfs_rq, struct sched_entity *se) { /* * We are starting a new run period: */ se->exec_start = rq_clock_task(rq_of(cfs_rq)); } /************************************************** * Scheduling class queueing methods: */ static inline bool is_core_idle(int cpu) { #ifdef CONFIG_SCHED_SMT int sibling; for_each_cpu(sibling, cpu_smt_mask(cpu)) { if (cpu == sibling) continue; if (!idle_cpu(sibling)) return false; } #endif return true; } #ifdef CONFIG_NUMA #define NUMA_IMBALANCE_MIN 2 static inline long adjust_numa_imbalance(int imbalance, int dst_running, int imb_numa_nr) { /* * Allow a NUMA imbalance if busy CPUs is less than the maximum * threshold. Above this threshold, individual tasks may be contending * for both memory bandwidth and any shared HT resources. This is an * approximation as the number of running tasks may not be related to * the number of busy CPUs due to sched_setaffinity. */ if (dst_running > imb_numa_nr) return imbalance; /* * Allow a small imbalance based on a simple pair of communicating * tasks that remain local when the destination is lightly loaded. */ if (imbalance <= NUMA_IMBALANCE_MIN) return 0; return imbalance; } #endif /* CONFIG_NUMA */ #ifdef CONFIG_NUMA_BALANCING /* * Approximate time to scan a full NUMA task in ms. The task scan period is * calculated based on the tasks virtual memory size and * numa_balancing_scan_size. */ unsigned int sysctl_numa_balancing_scan_period_min = 1000; unsigned int sysctl_numa_balancing_scan_period_max = 60000; /* Portion of address space to scan in MB */ unsigned int sysctl_numa_balancing_scan_size = 256; /* Scan @scan_size MB every @scan_period after an initial @scan_delay in ms */ unsigned int sysctl_numa_balancing_scan_delay = 1000; /* The page with hint page fault latency < threshold in ms is considered hot */ unsigned int sysctl_numa_balancing_hot_threshold = MSEC_PER_SEC; struct numa_group { refcount_t refcount; spinlock_t lock; /* nr_tasks, tasks */ int nr_tasks; pid_t gid; int active_nodes; struct rcu_head rcu; unsigned long total_faults; unsigned long max_faults_cpu; /* * faults[] array is split into two regions: faults_mem and faults_cpu. * * Faults_cpu is used to decide whether memory should move * towards the CPU. As a consequence, these stats are weighted * more by CPU use than by memory faults. */ unsigned long faults[]; }; /* * For functions that can be called in multiple contexts that permit reading * ->numa_group (see struct task_struct for locking rules). */ static struct numa_group *deref_task_numa_group(struct task_struct *p) { return rcu_dereference_check(p->numa_group, p == current || (lockdep_is_held(__rq_lockp(task_rq(p))) && !READ_ONCE(p->on_cpu))); } static struct numa_group *deref_curr_numa_group(struct task_struct *p) { return rcu_dereference_protected(p->numa_group, p == current); } static inline unsigned long group_faults_priv(struct numa_group *ng); static inline unsigned long group_faults_shared(struct numa_group *ng); static unsigned int task_nr_scan_windows(struct task_struct *p) { unsigned long rss = 0; unsigned long nr_scan_pages; /* * Calculations based on RSS as non-present and empty pages are skipped * by the PTE scanner and NUMA hinting faults should be trapped based * on resident pages */ nr_scan_pages = sysctl_numa_balancing_scan_size << (20 - PAGE_SHIFT); rss = get_mm_rss(p->mm); if (!rss) rss = nr_scan_pages; rss = round_up(rss, nr_scan_pages); return rss / nr_scan_pages; } /* For sanity's sake, never scan more PTEs than MAX_SCAN_WINDOW MB/sec. */ #define MAX_SCAN_WINDOW 2560 static unsigned int task_scan_min(struct task_struct *p) { unsigned int scan_size = READ_ONCE(sysctl_numa_balancing_scan_size); unsigned int scan, floor; unsigned int windows = 1; if (scan_size < MAX_SCAN_WINDOW) windows = MAX_SCAN_WINDOW / scan_size; floor = 1000 / windows; scan = sysctl_numa_balancing_scan_period_min / task_nr_scan_windows(p); return max_t(unsigned int, floor, scan); } static unsigned int task_scan_start(struct task_struct *p) { unsigned long smin = task_scan_min(p); unsigned long period = smin; struct numa_group *ng; /* Scale the maximum scan period with the amount of shared memory. */ rcu_read_lock(); ng = rcu_dereference(p->numa_group); if (ng) { unsigned long shared = group_faults_shared(ng); unsigned long private = group_faults_priv(ng); period *= refcount_read(&ng->refcount); period *= shared + 1; period /= private + shared + 1; } rcu_read_unlock(); return max(smin, period); } static unsigned int task_scan_max(struct task_struct *p) { unsigned long smin = task_scan_min(p); unsigned long smax; struct numa_group *ng; /* Watch for min being lower than max due to floor calculations */ smax = sysctl_numa_balancing_scan_period_max / task_nr_scan_windows(p); /* Scale the maximum scan period with the amount of shared memory. */ ng = deref_curr_numa_group(p); if (ng) { unsigned long shared = group_faults_shared(ng); unsigned long private = group_faults_priv(ng); unsigned long period = smax; period *= refcount_read(&ng->refcount); period *= shared + 1; period /= private + shared + 1; smax = max(smax, period); } return max(smin, smax); } static void account_numa_enqueue(struct rq *rq, struct task_struct *p) { rq->nr_numa_running += (p->numa_preferred_nid != NUMA_NO_NODE); rq->nr_preferred_running += (p->numa_preferred_nid == task_node(p)); } static void account_numa_dequeue(struct rq *rq, struct task_struct *p) { rq->nr_numa_running -= (p->numa_preferred_nid != NUMA_NO_NODE); rq->nr_preferred_running -= (p->numa_preferred_nid == task_node(p)); } /* Shared or private faults. */ #define NR_NUMA_HINT_FAULT_TYPES 2 /* Memory and CPU locality */ #define NR_NUMA_HINT_FAULT_STATS (NR_NUMA_HINT_FAULT_TYPES * 2) /* Averaged statistics, and temporary buffers. */ #define NR_NUMA_HINT_FAULT_BUCKETS (NR_NUMA_HINT_FAULT_STATS * 2) pid_t task_numa_group_id(struct task_struct *p) { struct numa_group *ng; pid_t gid = 0; rcu_read_lock(); ng = rcu_dereference(p->numa_group); if (ng) gid = ng->gid; rcu_read_unlock(); return gid; } /* * The averaged statistics, shared & private, memory & CPU, * occupy the first half of the array. The second half of the * array is for current counters, which are averaged into the * first set by task_numa_placement. */ static inline int task_faults_idx(enum numa_faults_stats s, int nid, int priv) { return NR_NUMA_HINT_FAULT_TYPES * (s * nr_node_ids + nid) + priv; } static inline unsigned long task_faults(struct task_struct *p, int nid) { if (!p->numa_faults) return 0; return p->numa_faults[task_faults_idx(NUMA_MEM, nid, 0)] + p->numa_faults[task_faults_idx(NUMA_MEM, nid, 1)]; } static inline unsigned long group_faults(struct task_struct *p, int nid) { struct numa_group *ng = deref_task_numa_group(p); if (!ng) return 0; return ng->faults[task_faults_idx(NUMA_MEM, nid, 0)] + ng->faults[task_faults_idx(NUMA_MEM, nid, 1)]; } static inline unsigned long group_faults_cpu(struct numa_group *group, int nid) { return group->faults[task_faults_idx(NUMA_CPU, nid, 0)] + group->faults[task_faults_idx(NUMA_CPU, nid, 1)]; } static inline unsigned long group_faults_priv(struct numa_group *ng) { unsigned long faults = 0; int node; for_each_online_node(node) { faults += ng->faults[task_faults_idx(NUMA_MEM, node, 1)]; } return faults; } static inline unsigned long group_faults_shared(struct numa_group *ng) { unsigned long faults = 0; int node; for_each_online_node(node) { faults += ng->faults[task_faults_idx(NUMA_MEM, node, 0)]; } return faults; } /* * A node triggering more than 1/3 as many NUMA faults as the maximum is * considered part of a numa group's pseudo-interleaving set. Migrations * between these nodes are slowed down, to allow things to settle down. */ #define ACTIVE_NODE_FRACTION 3 static bool numa_is_active_node(int nid, struct numa_group *ng) { return group_faults_cpu(ng, nid) * ACTIVE_NODE_FRACTION > ng->max_faults_cpu; } /* Handle placement on systems where not all nodes are directly connected. */ static unsigned long score_nearby_nodes(struct task_struct *p, int nid, int lim_dist, bool task) { unsigned long score = 0; int node, max_dist; /* * All nodes are directly connected, and the same distance * from each other. No need for fancy placement algorithms. */ if (sched_numa_topology_type == NUMA_DIRECT) return 0; /* sched_max_numa_distance may be changed in parallel. */ max_dist = READ_ONCE(sched_max_numa_distance); /* * This code is called for each node, introducing N^2 complexity, * which should be ok given the number of nodes rarely exceeds 8. */ for_each_online_node(node) { unsigned long faults; int dist = node_distance(nid, node); /* * The furthest away nodes in the system are not interesting * for placement; nid was already counted. */ if (dist >= max_dist || node == nid) continue; /* * On systems with a backplane NUMA topology, compare groups * of nodes, and move tasks towards the group with the most * memory accesses. When comparing two nodes at distance * "hoplimit", only nodes closer by than "hoplimit" are part * of each group. Skip other nodes. */ if (sched_numa_topology_type == NUMA_BACKPLANE && dist >= lim_dist) continue; /* Add up the faults from nearby nodes. */ if (task) faults = task_faults(p, node); else faults = group_faults(p, node); /* * On systems with a glueless mesh NUMA topology, there are * no fixed "groups of nodes". Instead, nodes that are not * directly connected bounce traffic through intermediate * nodes; a numa_group can occupy any set of nodes. * The further away a node is, the less the faults count. * This seems to result in good task placement. */ if (sched_numa_topology_type == NUMA_GLUELESS_MESH) { faults *= (max_dist - dist); faults /= (max_dist - LOCAL_DISTANCE); } score += faults; } return score; } /* * These return the fraction of accesses done by a particular task, or * task group, on a particular numa node. The group weight is given a * larger multiplier, in order to group tasks together that are almost * evenly spread out between numa nodes. */ static inline unsigned long task_weight(struct task_struct *p, int nid, int dist) { unsigned long faults, total_faults; if (!p->numa_faults) return 0; total_faults = p->total_numa_faults; if (!total_faults) return 0; faults = task_faults(p, nid); faults += score_nearby_nodes(p, nid, dist, true); return 1000 * faults / total_faults; } static inline unsigned long group_weight(struct task_struct *p, int nid, int dist) { struct numa_group *ng = deref_task_numa_group(p); unsigned long faults, total_faults; if (!ng) return 0; total_faults = ng->total_faults; if (!total_faults) return 0; faults = group_faults(p, nid); faults += score_nearby_nodes(p, nid, dist, false); return 1000 * faults / total_faults; } /* * If memory tiering mode is enabled, cpupid of slow memory page is * used to record scan time instead of CPU and PID. When tiering mode * is disabled at run time, the scan time (in cpupid) will be * interpreted as CPU and PID. So CPU needs to be checked to avoid to * access out of array bound. */ static inline bool cpupid_valid(int cpupid) { return cpupid_to_cpu(cpupid) < nr_cpu_ids; } /* * For memory tiering mode, if there are enough free pages (more than * enough watermark defined here) in fast memory node, to take full * advantage of fast memory capacity, all recently accessed slow * memory pages will be migrated to fast memory node without * considering hot threshold. */ static bool pgdat_free_space_enough(struct pglist_data *pgdat) { int z; unsigned long enough_wmark; enough_wmark = max(1UL * 1024 * 1024 * 1024 >> PAGE_SHIFT, pgdat->node_present_pages >> 4); for (z = pgdat->nr_zones - 1; z >= 0; z--) { struct zone *zone = pgdat->node_zones + z; if (!populated_zone(zone)) continue; if (zone_watermark_ok(zone, 0, wmark_pages(zone, WMARK_PROMO) + enough_wmark, ZONE_MOVABLE, 0)) return true; } return false; } /* * For memory tiering mode, when page tables are scanned, the scan * time will be recorded in struct page in addition to make page * PROT_NONE for slow memory page. So when the page is accessed, in * hint page fault handler, the hint page fault latency is calculated * via, * * hint page fault latency = hint page fault time - scan time * * The smaller the hint page fault latency, the higher the possibility * for the page to be hot. */ static int numa_hint_fault_latency(struct folio *folio) { int last_time, time; time = jiffies_to_msecs(jiffies); last_time = folio_xchg_access_time(folio, time); return (time - last_time) & PAGE_ACCESS_TIME_MASK; } /* * For memory tiering mode, too high promotion/demotion throughput may * hurt application latency. So we provide a mechanism to rate limit * the number of pages that are tried to be promoted. */ static bool numa_promotion_rate_limit(struct pglist_data *pgdat, unsigned long rate_limit, int nr) { unsigned long nr_cand; unsigned int now, start; now = jiffies_to_msecs(jiffies); mod_node_page_state(pgdat, PGPROMOTE_CANDIDATE, nr); nr_cand = node_page_state(pgdat, PGPROMOTE_CANDIDATE); start = pgdat->nbp_rl_start; if (now - start > MSEC_PER_SEC && cmpxchg(&pgdat->nbp_rl_start, start, now) == start) pgdat->nbp_rl_nr_cand = nr_cand; if (nr_cand - pgdat->nbp_rl_nr_cand >= rate_limit) return true; return false; } #define NUMA_MIGRATION_ADJUST_STEPS 16 static void numa_promotion_adjust_threshold(struct pglist_data *pgdat, unsigned long rate_limit, unsigned int ref_th) { unsigned int now, start, th_period, unit_th, th; unsigned long nr_cand, ref_cand, diff_cand; now = jiffies_to_msecs(jiffies); th_period = sysctl_numa_balancing_scan_period_max; start = pgdat->nbp_th_start; if (now - start > th_period && cmpxchg(&pgdat->nbp_th_start, start, now) == start) { ref_cand = rate_limit * sysctl_numa_balancing_scan_period_max / MSEC_PER_SEC; nr_cand = node_page_state(pgdat, PGPROMOTE_CANDIDATE); diff_cand = nr_cand - pgdat->nbp_th_nr_cand; unit_th = ref_th * 2 / NUMA_MIGRATION_ADJUST_STEPS; th = pgdat->nbp_threshold ? : ref_th; if (diff_cand > ref_cand * 11 / 10) th = max(th - unit_th, unit_th); else if (diff_cand < ref_cand * 9 / 10) th = min(th + unit_th, ref_th * 2); pgdat->nbp_th_nr_cand = nr_cand; pgdat->nbp_threshold = th; } } bool should_numa_migrate_memory(struct task_struct *p, struct folio *folio, int src_nid, int dst_cpu) { struct numa_group *ng = deref_curr_numa_group(p); int dst_nid = cpu_to_node(dst_cpu); int last_cpupid, this_cpupid; /* * The pages in slow memory node should be migrated according * to hot/cold instead of private/shared. */ if (sysctl_numa_balancing_mode & NUMA_BALANCING_MEMORY_TIERING && !node_is_toptier(src_nid)) { struct pglist_data *pgdat; unsigned long rate_limit; unsigned int latency, th, def_th; pgdat = NODE_DATA(dst_nid); if (pgdat_free_space_enough(pgdat)) { /* workload changed, reset hot threshold */ pgdat->nbp_threshold = 0; return true; } def_th = sysctl_numa_balancing_hot_threshold; rate_limit = sysctl_numa_balancing_promote_rate_limit << \ (20 - PAGE_SHIFT); numa_promotion_adjust_threshold(pgdat, rate_limit, def_th); th = pgdat->nbp_threshold ? : def_th; latency = numa_hint_fault_latency(folio); if (latency >= th) return false; return !numa_promotion_rate_limit(pgdat, rate_limit, folio_nr_pages(folio)); } this_cpupid = cpu_pid_to_cpupid(dst_cpu, current->pid); last_cpupid = folio_xchg_last_cpupid(folio, this_cpupid); if (!(sysctl_numa_balancing_mode & NUMA_BALANCING_MEMORY_TIERING) && !node_is_toptier(src_nid) && !cpupid_valid(last_cpupid)) return false; /* * Allow first faults or private faults to migrate immediately early in * the lifetime of a task. The magic number 4 is based on waiting for * two full passes of the "multi-stage node selection" test that is * executed below. */ if ((p->numa_preferred_nid == NUMA_NO_NODE || p->numa_scan_seq <= 4) && (cpupid_pid_unset(last_cpupid) || cpupid_match_pid(p, last_cpupid))) return true; /* * Multi-stage node selection is used in conjunction with a periodic * migration fault to build a temporal task<->page relation. By using * a two-stage filter we remove short/unlikely relations. * * Using P(p) ~ n_p / n_t as per frequentist probability, we can equate * a task's usage of a particular page (n_p) per total usage of this * page (n_t) (in a given time-span) to a probability. * * Our periodic faults will sample this probability and getting the * same result twice in a row, given these samples are fully * independent, is then given by P(n)^2, provided our sample period * is sufficiently short compared to the usage pattern. * * This quadric squishes small probabilities, making it less likely we * act on an unlikely task<->page relation. */ if (!cpupid_pid_unset(last_cpupid) && cpupid_to_nid(last_cpupid) != dst_nid) return false; /* Always allow migrate on private faults */ if (cpupid_match_pid(p, last_cpupid)) return true; /* A shared fault, but p->numa_group has not been set up yet. */ if (!ng) return true; /* * Destination node is much more heavily used than the source * node? Allow migration. */ if (group_faults_cpu(ng, dst_nid) > group_faults_cpu(ng, src_nid) * ACTIVE_NODE_FRACTION) return true; /* * Distribute memory according to CPU & memory use on each node, * with 3/4 hysteresis to avoid unnecessary memory migrations: * * faults_cpu(dst) 3 faults_cpu(src) * --------------- * - > --------------- * faults_mem(dst) 4 faults_mem(src) */ return group_faults_cpu(ng, dst_nid) * group_faults(p, src_nid) * 3 > group_faults_cpu(ng, src_nid) * group_faults(p, dst_nid) * 4; } /* * 'numa_type' describes the node at the moment of load balancing. */ enum numa_type { /* The node has spare capacity that can be used to run more tasks. */ node_has_spare = 0, /* * The node is fully used and the tasks don't compete for more CPU * cycles. Nevertheless, some tasks might wait before running. */ node_fully_busy, /* * The node is overloaded and can't provide expected CPU cycles to all * tasks. */ node_overloaded }; /* Cached statistics for all CPUs within a node */ struct numa_stats { unsigned long load; unsigned long runnable; unsigned long util; /* Total compute capacity of CPUs on a node */ unsigned long compute_capacity; unsigned int nr_running; unsigned int weight; enum numa_type node_type; int idle_cpu; }; struct task_numa_env { struct task_struct *p; int src_cpu, src_nid; int dst_cpu, dst_nid; int imb_numa_nr; struct numa_stats src_stats, dst_stats; int imbalance_pct; int dist; struct task_struct *best_task; long best_imp; int best_cpu; }; static unsigned long cpu_load(struct rq *rq); static unsigned long cpu_runnable(struct rq *rq); static inline enum numa_type numa_classify(unsigned int imbalance_pct, struct numa_stats *ns) { if ((ns->nr_running > ns->weight) && (((ns->compute_capacity * 100) < (ns->util * imbalance_pct)) || ((ns->compute_capacity * imbalance_pct) < (ns->runnable * 100)))) return node_overloaded; if ((ns->nr_running < ns->weight) || (((ns->compute_capacity * 100) > (ns->util * imbalance_pct)) && ((ns->compute_capacity * imbalance_pct) > (ns->runnable * 100)))) return node_has_spare; return node_fully_busy; } #ifdef CONFIG_SCHED_SMT /* Forward declarations of select_idle_sibling helpers */ static inline bool test_idle_cores(int cpu); static inline int numa_idle_core(int idle_core, int cpu) { if (!static_branch_likely(&sched_smt_present) || idle_core >= 0 || !test_idle_cores(cpu)) return idle_core; /* * Prefer cores instead of packing HT siblings * and triggering future load balancing. */ if (is_core_idle(cpu)) idle_core = cpu; return idle_core; } #else static inline int numa_idle_core(int idle_core, int cpu) { return idle_core; } #endif /* * Gather all necessary information to make NUMA balancing placement * decisions that are compatible with standard load balancer. This * borrows code and logic from update_sg_lb_stats but sharing a * common implementation is impractical. */ static void update_numa_stats(struct task_numa_env *env, struct numa_stats *ns, int nid, bool find_idle) { int cpu, idle_core = -1; memset(ns, 0, sizeof(*ns)); ns->idle_cpu = -1; rcu_read_lock(); for_each_cpu(cpu, cpumask_of_node(nid)) { struct rq *rq = cpu_rq(cpu); ns->load += cpu_load(rq); ns->runnable += cpu_runnable(rq); ns->util += cpu_util_cfs(cpu); ns->nr_running += rq->cfs.h_nr_running; ns->compute_capacity += capacity_of(cpu); if (find_idle && idle_core < 0 && !rq->nr_running && idle_cpu(cpu)) { if (READ_ONCE(rq->numa_migrate_on) || !cpumask_test_cpu(cpu, env->p->cpus_ptr)) continue; if (ns->idle_cpu == -1) ns->idle_cpu = cpu; idle_core = numa_idle_core(idle_core, cpu); } } rcu_read_unlock(); ns->weight = cpumask_weight(cpumask_of_node(nid)); ns->node_type = numa_classify(env->imbalance_pct, ns); if (idle_core >= 0) ns->idle_cpu = idle_core; } static void task_numa_assign(struct task_numa_env *env, struct task_struct *p, long imp) { struct rq *rq = cpu_rq(env->dst_cpu); /* Check if run-queue part of active NUMA balance. */ if (env->best_cpu != env->dst_cpu && xchg(&rq->numa_migrate_on, 1)) { int cpu; int start = env->dst_cpu; /* Find alternative idle CPU. */ for_each_cpu_wrap(cpu, cpumask_of_node(env->dst_nid), start + 1) { if (cpu == env->best_cpu || !idle_cpu(cpu) || !cpumask_test_cpu(cpu, env->p->cpus_ptr)) { continue; } env->dst_cpu = cpu; rq = cpu_rq(env->dst_cpu); if (!xchg(&rq->numa_migrate_on, 1)) goto assign; } /* Failed to find an alternative idle CPU */ return; } assign: /* * Clear previous best_cpu/rq numa-migrate flag, since task now * found a better CPU to move/swap. */ if (env->best_cpu != -1 && env->best_cpu != env->dst_cpu) { rq = cpu_rq(env->best_cpu); WRITE_ONCE(rq->numa_migrate_on, 0); } if (env->best_task) put_task_struct(env->best_task); if (p) get_task_struct(p); env->best_task = p; env->best_imp = imp; env->best_cpu = env->dst_cpu; } static bool load_too_imbalanced(long src_load, long dst_load, struct task_numa_env *env) { long imb, old_imb; long orig_src_load, orig_dst_load; long src_capacity, dst_capacity; /* * The load is corrected for the CPU capacity available on each node. * * src_load dst_load * ------------ vs --------- * src_capacity dst_capacity */ src_capacity = env->src_stats.compute_capacity; dst_capacity = env->dst_stats.compute_capacity; imb = abs(dst_load * src_capacity - src_load * dst_capacity); orig_src_load = env->src_stats.load; orig_dst_load = env->dst_stats.load; old_imb = abs(orig_dst_load * src_capacity - orig_src_load * dst_capacity); /* Would this change make things worse? */ return (imb > old_imb); } /* * Maximum NUMA importance can be 1998 (2*999); * SMALLIMP @ 30 would be close to 1998/64. * Used to deter task migration. */ #define SMALLIMP 30 /* * This checks if the overall compute and NUMA accesses of the system would * be improved if the source tasks was migrated to the target dst_cpu taking * into account that it might be best if task running on the dst_cpu should * be exchanged with the source task */ static bool task_numa_compare(struct task_numa_env *env, long taskimp, long groupimp, bool maymove) { struct numa_group *cur_ng, *p_ng = deref_curr_numa_group(env->p); struct rq *dst_rq = cpu_rq(env->dst_cpu); long imp = p_ng ? groupimp : taskimp; struct task_struct *cur; long src_load, dst_load; int dist = env->dist; long moveimp = imp; long load; bool stopsearch = false; if (READ_ONCE(dst_rq->numa_migrate_on)) return false; rcu_read_lock(); cur = rcu_dereference(dst_rq->curr); if (cur && ((cur->flags & PF_EXITING) || is_idle_task(cur))) cur = NULL; /* * Because we have preemption enabled we can get migrated around and * end try selecting ourselves (current == env->p) as a swap candidate. */ if (cur == env->p) { stopsearch = true; goto unlock; } if (!cur) { if (maymove && moveimp >= env->best_imp) goto assign; else goto unlock; } /* Skip this swap candidate if cannot move to the source cpu. */ if (!cpumask_test_cpu(env->src_cpu, cur->cpus_ptr)) goto unlock; /* * Skip this swap candidate if it is not moving to its preferred * node and the best task is. */ if (env->best_task && env->best_task->numa_preferred_nid == env->src_nid && cur->numa_preferred_nid != env->src_nid) { goto unlock; } /* * "imp" is the fault differential for the source task between the * source and destination node. Calculate the total differential for * the source task and potential destination task. The more negative * the value is, the more remote accesses that would be expected to * be incurred if the tasks were swapped. * * If dst and source tasks are in the same NUMA group, or not * in any group then look only at task weights. */ cur_ng = rcu_dereference(cur->numa_group); if (cur_ng == p_ng) { /* * Do not swap within a group or between tasks that have * no group if there is spare capacity. Swapping does * not address the load imbalance and helps one task at * the cost of punishing another. */ if (env->dst_stats.node_type == node_has_spare) goto unlock; imp = taskimp + task_weight(cur, env->src_nid, dist) - task_weight(cur, env->dst_nid, dist); /* * Add some hysteresis to prevent swapping the * tasks within a group over tiny differences. */ if (cur_ng) imp -= imp / 16; } else { /* * Compare the group weights. If a task is all by itself * (not part of a group), use the task weight instead. */ if (cur_ng && p_ng) imp += group_weight(cur, env->src_nid, dist) - group_weight(cur, env->dst_nid, dist); else imp += task_weight(cur, env->src_nid, dist) - task_weight(cur, env->dst_nid, dist); } /* Discourage picking a task already on its preferred node */ if (cur->numa_preferred_nid == env->dst_nid) imp -= imp / 16; /* * Encourage picking a task that moves to its preferred node. * This potentially makes imp larger than it's maximum of * 1998 (see SMALLIMP and task_weight for why) but in this * case, it does not matter. */ if (cur->numa_preferred_nid == env->src_nid) imp += imp / 8; if (maymove && moveimp > imp && moveimp > env->best_imp) { imp = moveimp; cur = NULL; goto assign; } /* * Prefer swapping with a task moving to its preferred node over a * task that is not. */ if (env->best_task && cur->numa_preferred_nid == env->src_nid && env->best_task->numa_preferred_nid != env->src_nid) { goto assign; } /* * If the NUMA importance is less than SMALLIMP, * task migration might only result in ping pong * of tasks and also hurt performance due to cache * misses. */ if (imp < SMALLIMP || imp <= env->best_imp + SMALLIMP / 2) goto unlock; /* * In the overloaded case, try and keep the load balanced. */ load = task_h_load(env->p) - task_h_load(cur); if (!load) goto assign; dst_load = env->dst_stats.load + load; src_load = env->src_stats.load - load; if (load_too_imbalanced(src_load, dst_load, env)) goto unlock; assign: /* Evaluate an idle CPU for a task numa move. */ if (!cur) { int cpu = env->dst_stats.idle_cpu; /* Nothing cached so current CPU went idle since the search. */ if (cpu < 0) cpu = env->dst_cpu; /* * If the CPU is no longer truly idle and the previous best CPU * is, keep using it. */ if (!idle_cpu(cpu) && env->best_cpu >= 0 && idle_cpu(env->best_cpu)) { cpu = env->best_cpu; } env->dst_cpu = cpu; } task_numa_assign(env, cur, imp); /* * If a move to idle is allowed because there is capacity or load * balance improves then stop the search. While a better swap * candidate may exist, a search is not free. */ if (maymove && !cur && env->best_cpu >= 0 && idle_cpu(env->best_cpu)) stopsearch = true; /* * If a swap candidate must be identified and the current best task * moves its preferred node then stop the search. */ if (!maymove && env->best_task && env->best_task->numa_preferred_nid == env->src_nid) { stopsearch = true; } unlock: rcu_read_unlock(); return stopsearch; } static void task_numa_find_cpu(struct task_numa_env *env, long taskimp, long groupimp) { bool maymove = false; int cpu; /* * If dst node has spare capacity, then check if there is an * imbalance that would be overruled by the load balancer. */ if (env->dst_stats.node_type == node_has_spare) { unsigned int imbalance; int src_running, dst_running; /* * Would movement cause an imbalance? Note that if src has * more running tasks that the imbalance is ignored as the * move improves the imbalance from the perspective of the * CPU load balancer. * */ src_running = env->src_stats.nr_running - 1; dst_running = env->dst_stats.nr_running + 1; imbalance = max(0, dst_running - src_running); imbalance = adjust_numa_imbalance(imbalance, dst_running, env->imb_numa_nr); /* Use idle CPU if there is no imbalance */ if (!imbalance) { maymove = true; if (env->dst_stats.idle_cpu >= 0) { env->dst_cpu = env->dst_stats.idle_cpu; task_numa_assign(env, NULL, 0); return; } } } else { long src_load, dst_load, load; /* * If the improvement from just moving env->p direction is better * than swapping tasks around, check if a move is possible. */ load = task_h_load(env->p); dst_load = env->dst_stats.load + load; src_load = env->src_stats.load - load; maymove = !load_too_imbalanced(src_load, dst_load, env); } for_each_cpu(cpu, cpumask_of_node(env->dst_nid)) { /* Skip this CPU if the source task cannot migrate */ if (!cpumask_test_cpu(cpu, env->p->cpus_ptr)) continue; env->dst_cpu = cpu; if (task_numa_compare(env, taskimp, groupimp, maymove)) break; } } static int task_numa_migrate(struct task_struct *p) { struct task_numa_env env = { .p = p, .src_cpu = task_cpu(p), .src_nid = task_node(p), .imbalance_pct = 112, .best_task = NULL, .best_imp = 0, .best_cpu = -1, }; unsigned long taskweight, groupweight; struct sched_domain *sd; long taskimp, groupimp; struct numa_group *ng; struct rq *best_rq; int nid, ret, dist; /* * Pick the lowest SD_NUMA domain, as that would have the smallest * imbalance and would be the first to start moving tasks about. * * And we want to avoid any moving of tasks about, as that would create * random movement of tasks -- counter the numa conditions we're trying * to satisfy here. */ rcu_read_lock(); sd = rcu_dereference(per_cpu(sd_numa, env.src_cpu)); if (sd) { env.imbalance_pct = 100 + (sd->imbalance_pct - 100) / 2; env.imb_numa_nr = sd->imb_numa_nr; } rcu_read_unlock(); /* * Cpusets can break the scheduler domain tree into smaller * balance domains, some of which do not cross NUMA boundaries. * Tasks that are "trapped" in such domains cannot be migrated * elsewhere, so there is no point in (re)trying. */ if (unlikely(!sd)) { sched_setnuma(p, task_node(p)); return -EINVAL; } env.dst_nid = p->numa_preferred_nid; dist = env.dist = node_distance(env.src_nid, env.dst_nid); taskweight = task_weight(p, env.src_nid, dist); groupweight = group_weight(p, env.src_nid, dist); update_numa_stats(&env, &env.src_stats, env.src_nid, false); taskimp = task_weight(p, env.dst_nid, dist) - taskweight; groupimp = group_weight(p, env.dst_nid, dist) - groupweight; update_numa_stats(&env, &env.dst_stats, env.dst_nid, true); /* Try to find a spot on the preferred nid. */ task_numa_find_cpu(&env, taskimp, groupimp); /* * Look at other nodes in these cases: * - there is no space available on the preferred_nid * - the task is part of a numa_group that is interleaved across * multiple NUMA nodes; in order to better consolidate the group, * we need to check other locations. */ ng = deref_curr_numa_group(p); if (env.best_cpu == -1 || (ng && ng->active_nodes > 1)) { for_each_node_state(nid, N_CPU) { if (nid == env.src_nid || nid == p->numa_preferred_nid) continue; dist = node_distance(env.src_nid, env.dst_nid); if (sched_numa_topology_type == NUMA_BACKPLANE && dist != env.dist) { taskweight = task_weight(p, env.src_nid, dist); groupweight = group_weight(p, env.src_nid, dist); } /* Only consider nodes where both task and groups benefit */ taskimp = task_weight(p, nid, dist) - taskweight; groupimp = group_weight(p, nid, dist) - groupweight; if (taskimp < 0 && groupimp < 0) continue; env.dist = dist; env.dst_nid = nid; update_numa_stats(&env, &env.dst_stats, env.dst_nid, true); task_numa_find_cpu(&env, taskimp, groupimp); } } /* * If the task is part of a workload that spans multiple NUMA nodes, * and is migrating into one of the workload's active nodes, remember * this node as the task's preferred numa node, so the workload can * settle down. * A task that migrated to a second choice node will be better off * trying for a better one later. Do not set the preferred node here. */ if (ng) { if (env.best_cpu == -1) nid = env.src_nid; else nid = cpu_to_node(env.best_cpu); if (nid != p->numa_preferred_nid) sched_setnuma(p, nid); } /* No better CPU than the current one was found. */ if (env.best_cpu == -1) { trace_sched_stick_numa(p, env.src_cpu, NULL, -1); return -EAGAIN; } best_rq = cpu_rq(env.best_cpu); if (env.best_task == NULL) { ret = migrate_task_to(p, env.best_cpu); WRITE_ONCE(best_rq->numa_migrate_on, 0); if (ret != 0) trace_sched_stick_numa(p, env.src_cpu, NULL, env.best_cpu); return ret; } ret = migrate_swap(p, env.best_task, env.best_cpu, env.src_cpu); WRITE_ONCE(best_rq->numa_migrate_on, 0); if (ret != 0) trace_sched_stick_numa(p, env.src_cpu, env.best_task, env.best_cpu); put_task_struct(env.best_task); return ret; } /* Attempt to migrate a task to a CPU on the preferred node. */ static void numa_migrate_preferred(struct task_struct *p) { unsigned long interval = HZ; /* This task has no NUMA fault statistics yet */ if (unlikely(p->numa_preferred_nid == NUMA_NO_NODE || !p->numa_faults)) return; /* Periodically retry migrating the task to the preferred node */ interval = min(interval, msecs_to_jiffies(p->numa_scan_period) / 16); p->numa_migrate_retry = jiffies + interval; /* Success if task is already running on preferred CPU */ if (task_node(p) == p->numa_preferred_nid) return; /* Otherwise, try migrate to a CPU on the preferred node */ task_numa_migrate(p); } /* * Find out how many nodes the workload is actively running on. Do this by * tracking the nodes from which NUMA hinting faults are triggered. This can * be different from the set of nodes where the workload's memory is currently * located. */ static void numa_group_count_active_nodes(struct numa_group *numa_group) { unsigned long faults, max_faults = 0; int nid, active_nodes = 0; for_each_node_state(nid, N_CPU) { faults = group_faults_cpu(numa_group, nid); if (faults > max_faults) max_faults = faults; } for_each_node_state(nid, N_CPU) { faults = group_faults_cpu(numa_group, nid); if (faults * ACTIVE_NODE_FRACTION > max_faults) active_nodes++; } numa_group->max_faults_cpu = max_faults; numa_group->active_nodes = active_nodes; } /* * When adapting the scan rate, the period is divided into NUMA_PERIOD_SLOTS * increments. The more local the fault statistics are, the higher the scan * period will be for the next scan window. If local/(local+remote) ratio is * below NUMA_PERIOD_THRESHOLD (where range of ratio is 1..NUMA_PERIOD_SLOTS) * the scan period will decrease. Aim for 70% local accesses. */ #define NUMA_PERIOD_SLOTS 10 #define NUMA_PERIOD_THRESHOLD 7 /* * Increase the scan period (slow down scanning) if the majority of * our memory is already on our local node, or if the majority of * the page accesses are shared with other processes. * Otherwise, decrease the scan period. */ static void update_task_scan_period(struct task_struct *p, unsigned long shared, unsigned long private) { unsigned int period_slot; int lr_ratio, ps_ratio; int diff; unsigned long remote = p->numa_faults_locality[0]; unsigned long local = p->numa_faults_locality[1]; /* * If there were no record hinting faults then either the task is * completely idle or all activity is in areas that are not of interest * to automatic numa balancing. Related to that, if there were failed * migration then it implies we are migrating too quickly or the local * node is overloaded. In either case, scan slower */ if (local + shared == 0 || p->numa_faults_locality[2]) { p->numa_scan_period = min(p->numa_scan_period_max, p->numa_scan_period << 1); p->mm->numa_next_scan = jiffies + msecs_to_jiffies(p->numa_scan_period); return; } /* * Prepare to scale scan period relative to the current period. * == NUMA_PERIOD_THRESHOLD scan period stays the same * < NUMA_PERIOD_THRESHOLD scan period decreases (scan faster) * >= NUMA_PERIOD_THRESHOLD scan period increases (scan slower) */ period_slot = DIV_ROUND_UP(p->numa_scan_period, NUMA_PERIOD_SLOTS); lr_ratio = (local * NUMA_PERIOD_SLOTS) / (local + remote); ps_ratio = (private * NUMA_PERIOD_SLOTS) / (private + shared); if (ps_ratio >= NUMA_PERIOD_THRESHOLD) { /* * Most memory accesses are local. There is no need to * do fast NUMA scanning, since memory is already local. */ int slot = ps_ratio - NUMA_PERIOD_THRESHOLD; if (!slot) slot = 1; diff = slot * period_slot; } else if (lr_ratio >= NUMA_PERIOD_THRESHOLD) { /* * Most memory accesses are shared with other tasks. * There is no point in continuing fast NUMA scanning, * since other tasks may just move the memory elsewhere. */ int slot = lr_ratio - NUMA_PERIOD_THRESHOLD; if (!slot) slot = 1; diff = slot * period_slot; } else { /* * Private memory faults exceed (SLOTS-THRESHOLD)/SLOTS, * yet they are not on the local NUMA node. Speed up * NUMA scanning to get the memory moved over. */ int ratio = max(lr_ratio, ps_ratio); diff = -(NUMA_PERIOD_THRESHOLD - ratio) * period_slot; } p->numa_scan_period = clamp(p->numa_scan_period + diff, task_scan_min(p), task_scan_max(p)); memset(p->numa_faults_locality, 0, sizeof(p->numa_faults_locality)); } /* * Get the fraction of time the task has been running since the last * NUMA placement cycle. The scheduler keeps similar statistics, but * decays those on a 32ms period, which is orders of magnitude off * from the dozens-of-seconds NUMA balancing period. Use the scheduler * stats only if the task is so new there are no NUMA statistics yet. */ static u64 numa_get_avg_runtime(struct task_struct *p, u64 *period) { u64 runtime, delta, now; /* Use the start of this time slice to avoid calculations. */ now = p->se.exec_start; runtime = p->se.sum_exec_runtime; if (p->last_task_numa_placement) { delta = runtime - p->last_sum_exec_runtime; *period = now - p->last_task_numa_placement; /* Avoid time going backwards, prevent potential divide error: */ if (unlikely((s64)*period < 0)) *period = 0; } else { delta = p->se.avg.load_sum; *period = LOAD_AVG_MAX; } p->last_sum_exec_runtime = runtime; p->last_task_numa_placement = now; return delta; } /* * Determine the preferred nid for a task in a numa_group. This needs to * be done in a way that produces consistent results with group_weight, * otherwise workloads might not converge. */ static int preferred_group_nid(struct task_struct *p, int nid) { nodemask_t nodes; int dist; /* Direct connections between all NUMA nodes. */ if (sched_numa_topology_type == NUMA_DIRECT) return nid; /* * On a system with glueless mesh NUMA topology, group_weight * scores nodes according to the number of NUMA hinting faults on * both the node itself, and on nearby nodes. */ if (sched_numa_topology_type == NUMA_GLUELESS_MESH) { unsigned long score, max_score = 0; int node, max_node = nid; dist = sched_max_numa_distance; for_each_node_state(node, N_CPU) { score = group_weight(p, node, dist); if (score > max_score) { max_score = score; max_node = node; } } return max_node; } /* * Finding the preferred nid in a system with NUMA backplane * interconnect topology is more involved. The goal is to locate * tasks from numa_groups near each other in the system, and * untangle workloads from different sides of the system. This requires * searching down the hierarchy of node groups, recursively searching * inside the highest scoring group of nodes. The nodemask tricks * keep the complexity of the search down. */ nodes = node_states[N_CPU]; for (dist = sched_max_numa_distance; dist > LOCAL_DISTANCE; dist--) { unsigned long max_faults = 0; nodemask_t max_group = NODE_MASK_NONE; int a, b; /* Are there nodes at this distance from each other? */ if (!find_numa_distance(dist)) continue; for_each_node_mask(a, nodes) { unsigned long faults = 0; nodemask_t this_group; nodes_clear(this_group); /* Sum group's NUMA faults; includes a==b case. */ for_each_node_mask(b, nodes) { if (node_distance(a, b) < dist) { faults += group_faults(p, b); node_set(b, this_group); node_clear(b, nodes); } } /* Remember the top group. */ if (faults > max_faults) { max_faults = faults; max_group = this_group; /* * subtle: at the smallest distance there is * just one node left in each "group", the * winner is the preferred nid. */ nid = a; } } /* Next round, evaluate the nodes within max_group. */ if (!max_faults) break; nodes = max_group; } return nid; } static void task_numa_placement(struct task_struct *p) { int seq, nid, max_nid = NUMA_NO_NODE; unsigned long max_faults = 0; unsigned long fault_types[2] = { 0, 0 }; unsigned long total_faults; u64 runtime, period; spinlock_t *group_lock = NULL; struct numa_group *ng; /* * The p->mm->numa_scan_seq field gets updated without * exclusive access. Use READ_ONCE() here to ensure * that the field is read in a single access: */ seq = READ_ONCE(p->mm->numa_scan_seq); if (p->numa_scan_seq == seq) return; p->numa_scan_seq = seq; p->numa_scan_period_max = task_scan_max(p); total_faults = p->numa_faults_locality[0] + p->numa_faults_locality[1]; runtime = numa_get_avg_runtime(p, &period); /* If the task is part of a group prevent parallel updates to group stats */ ng = deref_curr_numa_group(p); if (ng) { group_lock = &ng->lock; spin_lock_irq(group_lock); } /* Find the node with the highest number of faults */ for_each_online_node(nid) { /* Keep track of the offsets in numa_faults array */ int mem_idx, membuf_idx, cpu_idx, cpubuf_idx; unsigned long faults = 0, group_faults = 0; int priv; for (priv = 0; priv < NR_NUMA_HINT_FAULT_TYPES; priv++) { long diff, f_diff, f_weight; mem_idx = task_faults_idx(NUMA_MEM, nid, priv); membuf_idx = task_faults_idx(NUMA_MEMBUF, nid, priv); cpu_idx = task_faults_idx(NUMA_CPU, nid, priv); cpubuf_idx = task_faults_idx(NUMA_CPUBUF, nid, priv); /* Decay existing window, copy faults since last scan */ diff = p->numa_faults[membuf_idx] - p->numa_faults[mem_idx] / 2; fault_types[priv] += p->numa_faults[membuf_idx]; p->numa_faults[membuf_idx] = 0; /* * Normalize the faults_from, so all tasks in a group * count according to CPU use, instead of by the raw * number of faults. Tasks with little runtime have * little over-all impact on throughput, and thus their * faults are less important. */ f_weight = div64_u64(runtime << 16, period + 1); f_weight = (f_weight * p->numa_faults[cpubuf_idx]) / (total_faults + 1); f_diff = f_weight - p->numa_faults[cpu_idx] / 2; p->numa_faults[cpubuf_idx] = 0; p->numa_faults[mem_idx] += diff; p->numa_faults[cpu_idx] += f_diff; faults += p->numa_faults[mem_idx]; p->total_numa_faults += diff; if (ng) { /* * safe because we can only change our own group * * mem_idx represents the offset for a given * nid and priv in a specific region because it * is at the beginning of the numa_faults array. */ ng->faults[mem_idx] += diff; ng->faults[cpu_idx] += f_diff; ng->total_faults += diff; group_faults += ng->faults[mem_idx]; } } if (!ng) { if (faults > max_faults) { max_faults = faults; max_nid = nid; } } else if (group_faults > max_faults) { max_faults = group_faults; max_nid = nid; } } /* Cannot migrate task to CPU-less node */ max_nid = numa_nearest_node(max_nid, N_CPU); if (ng) { numa_group_count_active_nodes(ng); spin_unlock_irq(group_lock); max_nid = preferred_group_nid(p, max_nid); } if (max_faults) { /* Set the new preferred node */ if (max_nid != p->numa_preferred_nid) sched_setnuma(p, max_nid); } update_task_scan_period(p, fault_types[0], fault_types[1]); } static inline int get_numa_group(struct numa_group *grp) { return refcount_inc_not_zero(&grp->refcount); } static inline void put_numa_group(struct numa_group *grp) { if (refcount_dec_and_test(&grp->refcount)) kfree_rcu(grp, rcu); } static void task_numa_group(struct task_struct *p, int cpupid, int flags, int *priv) { struct numa_group *grp, *my_grp; struct task_struct *tsk; bool join = false; int cpu = cpupid_to_cpu(cpupid); int i; if (unlikely(!deref_curr_numa_group(p))) { unsigned int size = sizeof(struct numa_group) + NR_NUMA_HINT_FAULT_STATS * nr_node_ids * sizeof(unsigned long); grp = kzalloc(size, GFP_KERNEL | __GFP_NOWARN); if (!grp) return; refcount_set(&grp->refcount, 1); grp->active_nodes = 1; grp->max_faults_cpu = 0; spin_lock_init(&grp->lock); grp->gid = p->pid; for (i = 0; i < NR_NUMA_HINT_FAULT_STATS * nr_node_ids; i++) grp->faults[i] = p->numa_faults[i]; grp->total_faults = p->total_numa_faults; grp->nr_tasks++; rcu_assign_pointer(p->numa_group, grp); } rcu_read_lock(); tsk = READ_ONCE(cpu_rq(cpu)->curr); if (!cpupid_match_pid(tsk, cpupid)) goto no_join; grp = rcu_dereference(tsk->numa_group); if (!grp) goto no_join; my_grp = deref_curr_numa_group(p); if (grp == my_grp) goto no_join; /* * Only join the other group if its bigger; if we're the bigger group, * the other task will join us. */ if (my_grp->nr_tasks > grp->nr_tasks) goto no_join; /* * Tie-break on the grp address. */ if (my_grp->nr_tasks == grp->nr_tasks && my_grp > grp) goto no_join; /* Always join threads in the same process. */ if (tsk->mm == current->mm) join = true; /* Simple filter to avoid false positives due to PID collisions */ if (flags & TNF_SHARED) join = true; /* Update priv based on whether false sharing was detected */ *priv = !join; if (join && !get_numa_group(grp)) goto no_join; rcu_read_unlock(); if (!join) return; WARN_ON_ONCE(irqs_disabled()); double_lock_irq(&my_grp->lock, &grp->lock); for (i = 0; i < NR_NUMA_HINT_FAULT_STATS * nr_node_ids; i++) { my_grp->faults[i] -= p->numa_faults[i]; grp->faults[i] += p->numa_faults[i]; } my_grp->total_faults -= p->total_numa_faults; grp->total_faults += p->total_numa_faults; my_grp->nr_tasks--; grp->nr_tasks++; spin_unlock(&my_grp->lock); spin_unlock_irq(&grp->lock); rcu_assign_pointer(p->numa_group, grp); put_numa_group(my_grp); return; no_join: rcu_read_unlock(); return; } /* * Get rid of NUMA statistics associated with a task (either current or dead). * If @final is set, the task is dead and has reached refcount zero, so we can * safely free all relevant data structures. Otherwise, there might be * concurrent reads from places like load balancing and procfs, and we should * reset the data back to default state without freeing ->numa_faults. */ void task_numa_free(struct task_struct *p, bool final) { /* safe: p either is current or is being freed by current */ struct numa_group *grp = rcu_dereference_raw(p->numa_group); unsigned long *numa_faults = p->numa_faults; unsigned long flags; int i; if (!numa_faults) return; if (grp) { spin_lock_irqsave(&grp->lock, flags); for (i = 0; i < NR_NUMA_HINT_FAULT_STATS * nr_node_ids; i++) grp->faults[i] -= p->numa_faults[i]; grp->total_faults -= p->total_numa_faults; grp->nr_tasks--; spin_unlock_irqrestore(&grp->lock, flags); RCU_INIT_POINTER(p->numa_group, NULL); put_numa_group(grp); } if (final) { p->numa_faults = NULL; kfree(numa_faults); } else { p->total_numa_faults = 0; for (i = 0; i < NR_NUMA_HINT_FAULT_STATS * nr_node_ids; i++) numa_faults[i] = 0; } } /* * Got a PROT_NONE fault for a page on @node. */ void task_numa_fault(int last_cpupid, int mem_node, int pages, int flags) { struct task_struct *p = current; bool migrated = flags & TNF_MIGRATED; int cpu_node = task_node(current); int local = !!(flags & TNF_FAULT_LOCAL); struct numa_group *ng; int priv; if (!static_branch_likely(&sched_numa_balancing)) return; /* for example, ksmd faulting in a user's mm */ if (!p->mm) return; /* * NUMA faults statistics are unnecessary for the slow memory * node for memory tiering mode. */ if (!node_is_toptier(mem_node) && (sysctl_numa_balancing_mode & NUMA_BALANCING_MEMORY_TIERING || !cpupid_valid(last_cpupid))) return; /* Allocate buffer to track faults on a per-node basis */ if (unlikely(!p->numa_faults)) { int size = sizeof(*p->numa_faults) * NR_NUMA_HINT_FAULT_BUCKETS * nr_node_ids; p->numa_faults = kzalloc(size, GFP_KERNEL|__GFP_NOWARN); if (!p->numa_faults) return; p->total_numa_faults = 0; memset(p->numa_faults_locality, 0, sizeof(p->numa_faults_locality)); } /* * First accesses are treated as private, otherwise consider accesses * to be private if the accessing pid has not changed */ if (unlikely(last_cpupid == (-1 & LAST_CPUPID_MASK))) { priv = 1; } else { priv = cpupid_match_pid(p, last_cpupid); if (!priv && !(flags & TNF_NO_GROUP)) task_numa_group(p, last_cpupid, flags, &priv); } /* * If a workload spans multiple NUMA nodes, a shared fault that * occurs wholly within the set of nodes that the workload is * actively using should be counted as local. This allows the * scan rate to slow down when a workload has settled down. */ ng = deref_curr_numa_group(p); if (!priv && !local && ng && ng->active_nodes > 1 && numa_is_active_node(cpu_node, ng) && numa_is_active_node(mem_node, ng)) local = 1; /* * Retry to migrate task to preferred node periodically, in case it * previously failed, or the scheduler moved us. */ if (time_after(jiffies, p->numa_migrate_retry)) { task_numa_placement(p); numa_migrate_preferred(p); } if (migrated) p->numa_pages_migrated += pages; if (flags & TNF_MIGRATE_FAIL) p->numa_faults_locality[2] += pages; p->numa_faults[task_faults_idx(NUMA_MEMBUF, mem_node, priv)] += pages; p->numa_faults[task_faults_idx(NUMA_CPUBUF, cpu_node, priv)] += pages; p->numa_faults_locality[local] += pages; } static void reset_ptenuma_scan(struct task_struct *p) { /* * We only did a read acquisition of the mmap sem, so * p->mm->numa_scan_seq is written to without exclusive access * and the update is not guaranteed to be atomic. That's not * much of an issue though, since this is just used for * statistical sampling. Use READ_ONCE/WRITE_ONCE, which are not * expensive, to avoid any form of compiler optimizations: */ WRITE_ONCE(p->mm->numa_scan_seq, READ_ONCE(p->mm->numa_scan_seq) + 1); p->mm->numa_scan_offset = 0; } static bool vma_is_accessed(struct mm_struct *mm, struct vm_area_struct *vma) { unsigned long pids; /* * Allow unconditional access first two times, so that all the (pages) * of VMAs get prot_none fault introduced irrespective of accesses. * This is also done to avoid any side effect of task scanning * amplifying the unfairness of disjoint set of VMAs' access. */ if (READ_ONCE(current->mm->numa_scan_seq) < 2) return true; pids = vma->numab_state->pids_active[0] | vma->numab_state->pids_active[1]; if (test_bit(hash_32(current->pid, ilog2(BITS_PER_LONG)), &pids)) return true; /* * Complete a scan that has already started regardless of PID access, or * some VMAs may never be scanned in multi-threaded applications: */ if (mm->numa_scan_offset > vma->vm_start) { trace_sched_skip_vma_numa(mm, vma, NUMAB_SKIP_IGNORE_PID); return true; } return false; } #define VMA_PID_RESET_PERIOD (4 * sysctl_numa_balancing_scan_delay) /* * The expensive part of numa migration is done from task_work context. * Triggered from task_tick_numa(). */ static void task_numa_work(struct callback_head *work) { unsigned long migrate, next_scan, now = jiffies; struct task_struct *p = current; struct mm_struct *mm = p->mm; u64 runtime = p->se.sum_exec_runtime; struct vm_area_struct *vma; unsigned long start, end; unsigned long nr_pte_updates = 0; long pages, virtpages; struct vma_iterator vmi; bool vma_pids_skipped; bool vma_pids_forced = false; SCHED_WARN_ON(p != container_of(work, struct task_struct, numa_work)); work->next = work; /* * Who cares about NUMA placement when they're dying. * * NOTE: make sure not to dereference p->mm before this check, * exit_task_work() happens _after_ exit_mm() so we could be called * without p->mm even though we still had it when we enqueued this * work. */ if (p->flags & PF_EXITING) return; if (!mm->numa_next_scan) { mm->numa_next_scan = now + msecs_to_jiffies(sysctl_numa_balancing_scan_delay); } /* * Enforce maximal scan/migration frequency.. */ migrate = mm->numa_next_scan; if (time_before(now, migrate)) return; if (p->numa_scan_period == 0) { p->numa_scan_period_max = task_scan_max(p); p->numa_scan_period = task_scan_start(p); } next_scan = now + msecs_to_jiffies(p->numa_scan_period); if (!try_cmpxchg(&mm->numa_next_scan, &migrate, next_scan)) return; /* * Delay this task enough that another task of this mm will likely win * the next time around. */ p->node_stamp += 2 * TICK_NSEC; pages = sysctl_numa_balancing_scan_size; pages <<= 20 - PAGE_SHIFT; /* MB in pages */ virtpages = pages * 8; /* Scan up to this much virtual space */ if (!pages) return; if (!mmap_read_trylock(mm)) return; /* * VMAs are skipped if the current PID has not trapped a fault within * the VMA recently. Allow scanning to be forced if there is no * suitable VMA remaining. */ vma_pids_skipped = false; retry_pids: start = mm->numa_scan_offset; vma_iter_init(&vmi, mm, start); vma = vma_next(&vmi); if (!vma) { reset_ptenuma_scan(p); start = 0; vma_iter_set(&vmi, start); vma = vma_next(&vmi); } do { if (!vma_migratable(vma) || !vma_policy_mof(vma) || is_vm_hugetlb_page(vma) || (vma->vm_flags & VM_MIXEDMAP)) { trace_sched_skip_vma_numa(mm, vma, NUMAB_SKIP_UNSUITABLE); continue; } /* * Shared library pages mapped by multiple processes are not * migrated as it is expected they are cache replicated. Avoid * hinting faults in read-only file-backed mappings or the vdso * as migrating the pages will be of marginal benefit. */ if (!vma->vm_mm || (vma->vm_file && (vma->vm_flags & (VM_READ|VM_WRITE)) == (VM_READ))) { trace_sched_skip_vma_numa(mm, vma, NUMAB_SKIP_SHARED_RO); continue; } /* * Skip inaccessible VMAs to avoid any confusion between * PROT_NONE and NUMA hinting ptes */ if (!vma_is_accessible(vma)) { trace_sched_skip_vma_numa(mm, vma, NUMAB_SKIP_INACCESSIBLE); continue; } /* Initialise new per-VMA NUMAB state. */ if (!vma->numab_state) { vma->numab_state = kzalloc(sizeof(struct vma_numab_state), GFP_KERNEL); if (!vma->numab_state) continue; vma->numab_state->next_scan = now + msecs_to_jiffies(sysctl_numa_balancing_scan_delay); /* Reset happens after 4 times scan delay of scan start */ vma->numab_state->pids_active_reset = vma->numab_state->next_scan + msecs_to_jiffies(VMA_PID_RESET_PERIOD); /* * Ensure prev_scan_seq does not match numa_scan_seq, * to prevent VMAs being skipped prematurely on the * first scan: */ vma->numab_state->prev_scan_seq = mm->numa_scan_seq - 1; } /* * Scanning the VMA's of short lived tasks add more overhead. So * delay the scan for new VMAs. */ if (mm->numa_scan_seq && time_before(jiffies, vma->numab_state->next_scan)) { trace_sched_skip_vma_numa(mm, vma, NUMAB_SKIP_SCAN_DELAY); continue; } /* RESET access PIDs regularly for old VMAs. */ if (mm->numa_scan_seq && time_after(jiffies, vma->numab_state->pids_active_reset)) { vma->numab_state->pids_active_reset = vma->numab_state->pids_active_reset + msecs_to_jiffies(VMA_PID_RESET_PERIOD); vma->numab_state->pids_active[0] = READ_ONCE(vma->numab_state->pids_active[1]); vma->numab_state->pids_active[1] = 0; } /* Do not rescan VMAs twice within the same sequence. */ if (vma->numab_state->prev_scan_seq == mm->numa_scan_seq) { mm->numa_scan_offset = vma->vm_end; trace_sched_skip_vma_numa(mm, vma, NUMAB_SKIP_SEQ_COMPLETED); continue; } /* * Do not scan the VMA if task has not accessed it, unless no other * VMA candidate exists. */ if (!vma_pids_forced && !vma_is_accessed(mm, vma)) { vma_pids_skipped = true; trace_sched_skip_vma_numa(mm, vma, NUMAB_SKIP_PID_INACTIVE); continue; } do { start = max(start, vma->vm_start); end = ALIGN(start + (pages << PAGE_SHIFT), HPAGE_SIZE); end = min(end, vma->vm_end); nr_pte_updates = change_prot_numa(vma, start, end); /* * Try to scan sysctl_numa_balancing_size worth of * hpages that have at least one present PTE that * is not already pte-numa. If the VMA contains * areas that are unused or already full of prot_numa * PTEs, scan up to virtpages, to skip through those * areas faster. */ if (nr_pte_updates) pages -= (end - start) >> PAGE_SHIFT; virtpages -= (end - start) >> PAGE_SHIFT; start = end; if (pages <= 0 || virtpages <= 0) goto out; cond_resched(); } while (end != vma->vm_end); /* VMA scan is complete, do not scan until next sequence. */ vma->numab_state->prev_scan_seq = mm->numa_scan_seq; /* * Only force scan within one VMA at a time, to limit the * cost of scanning a potentially uninteresting VMA. */ if (vma_pids_forced) break; } for_each_vma(vmi, vma); /* * If no VMAs are remaining and VMAs were skipped due to the PID * not accessing the VMA previously, then force a scan to ensure * forward progress: */ if (!vma && !vma_pids_forced && vma_pids_skipped) { vma_pids_forced = true; goto retry_pids; } out: /* * It is possible to reach the end of the VMA list but the last few * VMAs are not guaranteed to the vma_migratable. If they are not, we * would find the !migratable VMA on the next scan but not reset the * scanner to the start so check it now. */ if (vma) mm->numa_scan_offset = start; else reset_ptenuma_scan(p); mmap_read_unlock(mm); /* * Make sure tasks use at least 32x as much time to run other code * than they used here, to limit NUMA PTE scanning overhead to 3% max. * Usually update_task_scan_period slows down scanning enough; on an * overloaded system we need to limit overhead on a per task basis. */ if (unlikely(p->se.sum_exec_runtime != runtime)) { u64 diff = p->se.sum_exec_runtime - runtime; p->node_stamp += 32 * diff; } } void init_numa_balancing(unsigned long clone_flags, struct task_struct *p) { int mm_users = 0; struct mm_struct *mm = p->mm; if (mm) { mm_users = atomic_read(&mm->mm_users); if (mm_users == 1) { mm->numa_next_scan = jiffies + msecs_to_jiffies(sysctl_numa_balancing_scan_delay); mm->numa_scan_seq = 0; } } p->node_stamp = 0; p->numa_scan_seq = mm ? mm->numa_scan_seq : 0; p->numa_scan_period = sysctl_numa_balancing_scan_delay; p->numa_migrate_retry = 0; /* Protect against double add, see task_tick_numa and task_numa_work */ p->numa_work.next = &p->numa_work; p->numa_faults = NULL; p->numa_pages_migrated = 0; p->total_numa_faults = 0; RCU_INIT_POINTER(p->numa_group, NULL); p->last_task_numa_placement = 0; p->last_sum_exec_runtime = 0; init_task_work(&p->numa_work, task_numa_work); /* New address space, reset the preferred nid */ if (!(clone_flags & CLONE_VM)) { p->numa_preferred_nid = NUMA_NO_NODE; return; } /* * New thread, keep existing numa_preferred_nid which should be copied * already by arch_dup_task_struct but stagger when scans start. */ if (mm) { unsigned int delay; delay = min_t(unsigned int, task_scan_max(current), current->numa_scan_period * mm_users * NSEC_PER_MSEC); delay += 2 * TICK_NSEC; p->node_stamp = delay; } } /* * Drive the periodic memory faults.. */ static void task_tick_numa(struct rq *rq, struct task_struct *curr) { struct callback_head *work = &curr->numa_work; u64 period, now; /* * We don't care about NUMA placement if we don't have memory. */ if (!curr->mm || (curr->flags & (PF_EXITING | PF_KTHREAD)) || work->next != work) return; /* * Using runtime rather than walltime has the dual advantage that * we (mostly) drive the selection from busy threads and that the * task needs to have done some actual work before we bother with * NUMA placement. */ now = curr->se.sum_exec_runtime; period = (u64)curr->numa_scan_period * NSEC_PER_MSEC; if (now > curr->node_stamp + period) { if (!curr->node_stamp) curr->numa_scan_period = task_scan_start(curr); curr->node_stamp += period; if (!time_before(jiffies, curr->mm->numa_next_scan)) task_work_add(curr, work, TWA_RESUME); } } static void update_scan_period(struct task_struct *p, int new_cpu) { int src_nid = cpu_to_node(task_cpu(p)); int dst_nid = cpu_to_node(new_cpu); if (!static_branch_likely(&sched_numa_balancing)) return; if (!p->mm || !p->numa_faults || (p->flags & PF_EXITING)) return; if (src_nid == dst_nid) return; /* * Allow resets if faults have been trapped before one scan * has completed. This is most likely due to a new task that * is pulled cross-node due to wakeups or load balancing. */ if (p->numa_scan_seq) { /* * Avoid scan adjustments if moving to the preferred * node or if the task was not previously running on * the preferred node. */ if (dst_nid == p->numa_preferred_nid || (p->numa_preferred_nid != NUMA_NO_NODE && src_nid != p->numa_preferred_nid)) return; } p->numa_scan_period = task_scan_start(p); } #else static void task_tick_numa(struct rq *rq, struct task_struct *curr) { } static inline void account_numa_enqueue(struct rq *rq, struct task_struct *p) { } static inline void account_numa_dequeue(struct rq *rq, struct task_struct *p) { } static inline void update_scan_period(struct task_struct *p, int new_cpu) { } #endif /* CONFIG_NUMA_BALANCING */ static void account_entity_enqueue(struct cfs_rq *cfs_rq, struct sched_entity *se) { update_load_add(&cfs_rq->load, se->load.weight); #ifdef CONFIG_SMP if (entity_is_task(se)) { struct rq *rq = rq_of(cfs_rq); account_numa_enqueue(rq, task_of(se)); list_add(&se->group_node, &rq->cfs_tasks); } #endif cfs_rq->nr_running++; if (se_is_idle(se)) cfs_rq->idle_nr_running++; } static void account_entity_dequeue(struct cfs_rq *cfs_rq, struct sched_entity *se) { update_load_sub(&cfs_rq->load, se->load.weight); #ifdef CONFIG_SMP if (entity_is_task(se)) { account_numa_dequeue(rq_of(cfs_rq), task_of(se)); list_del_init(&se->group_node); } #endif cfs_rq->nr_running--; if (se_is_idle(se)) cfs_rq->idle_nr_running--; } /* * Signed add and clamp on underflow. * * Explicitly do a load-store to ensure the intermediate value never hits * memory. This allows lockless observations without ever seeing the negative * values. */ #define add_positive(_ptr, _val) do { \ typeof(_ptr) ptr = (_ptr); \ typeof(_val) val = (_val); \ typeof(*ptr) res, var = READ_ONCE(*ptr); \ \ res = var + val; \ \ if (val < 0 && res > var) \ res = 0; \ \ WRITE_ONCE(*ptr, res); \ } while (0) /* * Unsigned subtract and clamp on underflow. * * Explicitly do a load-store to ensure the intermediate value never hits * memory. This allows lockless observations without ever seeing the negative * values. */ #define sub_positive(_ptr, _val) do { \ typeof(_ptr) ptr = (_ptr); \ typeof(*ptr) val = (_val); \ typeof(*ptr) res, var = READ_ONCE(*ptr); \ res = var - val; \ if (res > var) \ res = 0; \ WRITE_ONCE(*ptr, res); \ } while (0) /* * Remove and clamp on negative, from a local variable. * * A variant of sub_positive(), which does not use explicit load-store * and is thus optimized for local variable updates. */ #define lsub_positive(_ptr, _val) do { \ typeof(_ptr) ptr = (_ptr); \ *ptr -= min_t(typeof(*ptr), *ptr, _val); \ } while (0) #ifdef CONFIG_SMP static inline void enqueue_load_avg(struct cfs_rq *cfs_rq, struct sched_entity *se) { cfs_rq->avg.load_avg += se->avg.load_avg; cfs_rq->avg.load_sum += se_weight(se) * se->avg.load_sum; } static inline void dequeue_load_avg(struct cfs_rq *cfs_rq, struct sched_entity *se) { sub_positive(&cfs_rq->avg.load_avg, se->avg.load_avg); sub_positive(&cfs_rq->avg.load_sum, se_weight(se) * se->avg.load_sum); /* See update_cfs_rq_load_avg() */ cfs_rq->avg.load_sum = max_t(u32, cfs_rq->avg.load_sum, cfs_rq->avg.load_avg * PELT_MIN_DIVIDER); } #else static inline void enqueue_load_avg(struct cfs_rq *cfs_rq, struct sched_entity *se) { } static inline void dequeue_load_avg(struct cfs_rq *cfs_rq, struct sched_entity *se) { } #endif static void reweight_eevdf(struct cfs_rq *cfs_rq, struct sched_entity *se, unsigned long weight) { unsigned long old_weight = se->load.weight; u64 avruntime = avg_vruntime(cfs_rq); s64 vlag, vslice; /* * VRUNTIME * ======== * * COROLLARY #1: The virtual runtime of the entity needs to be * adjusted if re-weight at !0-lag point. * * Proof: For contradiction assume this is not true, so we can * re-weight without changing vruntime at !0-lag point. * * Weight VRuntime Avg-VRuntime * before w v V * after w' v' V' * * Since lag needs to be preserved through re-weight: * * lag = (V - v)*w = (V'- v')*w', where v = v' * ==> V' = (V - v)*w/w' + v (1) * * Let W be the total weight of the entities before reweight, * since V' is the new weighted average of entities: * * V' = (WV + w'v - wv) / (W + w' - w) (2) * * by using (1) & (2) we obtain: * * (WV + w'v - wv) / (W + w' - w) = (V - v)*w/w' + v * ==> (WV-Wv+Wv+w'v-wv)/(W+w'-w) = (V - v)*w/w' + v * ==> (WV - Wv)/(W + w' - w) + v = (V - v)*w/w' + v * ==> (V - v)*W/(W + w' - w) = (V - v)*w/w' (3) * * Since we are doing at !0-lag point which means V != v, we * can simplify (3): * * ==> W / (W + w' - w) = w / w' * ==> Ww' = Ww + ww' - ww * ==> W * (w' - w) = w * (w' - w) * ==> W = w (re-weight indicates w' != w) * * So the cfs_rq contains only one entity, hence vruntime of * the entity @v should always equal to the cfs_rq's weighted * average vruntime @V, which means we will always re-weight * at 0-lag point, thus breach assumption. Proof completed. * * * COROLLARY #2: Re-weight does NOT affect weighted average * vruntime of all the entities. * * Proof: According to corollary #1, Eq. (1) should be: * * (V - v)*w = (V' - v')*w' * ==> v' = V' - (V - v)*w/w' (4) * * According to the weighted average formula, we have: * * V' = (WV - wv + w'v') / (W - w + w') * = (WV - wv + w'(V' - (V - v)w/w')) / (W - w + w') * = (WV - wv + w'V' - Vw + wv) / (W - w + w') * = (WV + w'V' - Vw) / (W - w + w') * * ==> V'*(W - w + w') = WV + w'V' - Vw * ==> V' * (W - w) = (W - w) * V (5) * * If the entity is the only one in the cfs_rq, then reweight * always occurs at 0-lag point, so V won't change. Or else * there are other entities, hence W != w, then Eq. (5) turns * into V' = V. So V won't change in either case, proof done. * * * So according to corollary #1 & #2, the effect of re-weight * on vruntime should be: * * v' = V' - (V - v) * w / w' (4) * = V - (V - v) * w / w' * = V - vl * w / w' * = V - vl' */ if (avruntime != se->vruntime) { vlag = (s64)(avruntime - se->vruntime); vlag = div_s64(vlag * old_weight, weight); se->vruntime = avruntime - vlag; } /* * DEADLINE * ======== * * When the weight changes, the virtual time slope changes and * we should adjust the relative virtual deadline accordingly. * * d' = v' + (d - v)*w/w' * = V' - (V - v)*w/w' + (d - v)*w/w' * = V - (V - v)*w/w' + (d - v)*w/w' * = V + (d - V)*w/w' */ vslice = (s64)(se->deadline - avruntime); vslice = div_s64(vslice * old_weight, weight); se->deadline = avruntime + vslice; } static void reweight_entity(struct cfs_rq *cfs_rq, struct sched_entity *se, unsigned long weight) { bool curr = cfs_rq->curr == se; if (se->on_rq) { /* commit outstanding execution time */ if (curr) update_curr(cfs_rq); else __dequeue_entity(cfs_rq, se); update_load_sub(&cfs_rq->load, se->load.weight); } dequeue_load_avg(cfs_rq, se); if (!se->on_rq) { /* * Because we keep se->vlag = V - v_i, while: lag_i = w_i*(V - v_i), * we need to scale se->vlag when w_i changes. */ se->vlag = div_s64(se->vlag * se->load.weight, weight); } else { reweight_eevdf(cfs_rq, se, weight); } update_load_set(&se->load, weight); #ifdef CONFIG_SMP do { u32 divider = get_pelt_divider(&se->avg); se->avg.load_avg = div_u64(se_weight(se) * se->avg.load_sum, divider); } while (0); #endif enqueue_load_avg(cfs_rq, se); if (se->on_rq) { update_load_add(&cfs_rq->load, se->load.weight); if (!curr) { /* * The entity's vruntime has been adjusted, so let's check * whether the rq-wide min_vruntime needs updated too. Since * the calculations above require stable min_vruntime rather * than up-to-date one, we do the update at the end of the * reweight process. */ __enqueue_entity(cfs_rq, se); update_min_vruntime(cfs_rq); } } } void reweight_task(struct task_struct *p, int prio) { struct sched_entity *se = &p->se; struct cfs_rq *cfs_rq = cfs_rq_of(se); struct load_weight *load = &se->load; unsigned long weight = scale_load(sched_prio_to_weight[prio]); reweight_entity(cfs_rq, se, weight); load->inv_weight = sched_prio_to_wmult[prio]; } static inline int throttled_hierarchy(struct cfs_rq *cfs_rq); #ifdef CONFIG_FAIR_GROUP_SCHED #ifdef CONFIG_SMP /* * All this does is approximate the hierarchical proportion which includes that * global sum we all love to hate. * * That is, the weight of a group entity, is the proportional share of the * group weight based on the group runqueue weights. That is: * * tg->weight * grq->load.weight * ge->load.weight = ----------------------------- (1) * \Sum grq->load.weight * * Now, because computing that sum is prohibitively expensive to compute (been * there, done that) we approximate it with this average stuff. The average * moves slower and therefore the approximation is cheaper and more stable. * * So instead of the above, we substitute: * * grq->load.weight -> grq->avg.load_avg (2) * * which yields the following: * * tg->weight * grq->avg.load_avg * ge->load.weight = ------------------------------ (3) * tg->load_avg * * Where: tg->load_avg ~= \Sum grq->avg.load_avg * * That is shares_avg, and it is right (given the approximation (2)). * * The problem with it is that because the average is slow -- it was designed * to be exactly that of course -- this leads to transients in boundary * conditions. In specific, the case where the group was idle and we start the * one task. It takes time for our CPU's grq->avg.load_avg to build up, * yielding bad latency etc.. * * Now, in that special case (1) reduces to: * * tg->weight * grq->load.weight * ge->load.weight = ----------------------------- = tg->weight (4) * grp->load.weight * * That is, the sum collapses because all other CPUs are idle; the UP scenario. * * So what we do is modify our approximation (3) to approach (4) in the (near) * UP case, like: * * ge->load.weight = * * tg->weight * grq->load.weight * --------------------------------------------------- (5) * tg->load_avg - grq->avg.load_avg + grq->load.weight * * But because grq->load.weight can drop to 0, resulting in a divide by zero, * we need to use grq->avg.load_avg as its lower bound, which then gives: * * * tg->weight * grq->load.weight * ge->load.weight = ----------------------------- (6) * tg_load_avg' * * Where: * * tg_load_avg' = tg->load_avg - grq->avg.load_avg + * max(grq->load.weight, grq->avg.load_avg) * * And that is shares_weight and is icky. In the (near) UP case it approaches * (4) while in the normal case it approaches (3). It consistently * overestimates the ge->load.weight and therefore: * * \Sum ge->load.weight >= tg->weight * * hence icky! */ static long calc_group_shares(struct cfs_rq *cfs_rq) { long tg_weight, tg_shares, load, shares; struct task_group *tg = cfs_rq->tg; tg_shares = READ_ONCE(tg->shares); load = max(scale_load_down(cfs_rq->load.weight), cfs_rq->avg.load_avg); tg_weight = atomic_long_read(&tg->load_avg); /* Ensure tg_weight >= load */ tg_weight -= cfs_rq->tg_load_avg_contrib; tg_weight += load; shares = (tg_shares * load); if (tg_weight) shares /= tg_weight; /* * MIN_SHARES has to be unscaled here to support per-CPU partitioning * of a group with small tg->shares value. It is a floor value which is * assigned as a minimum load.weight to the sched_entity representing * the group on a CPU. * * E.g. on 64-bit for a group with tg->shares of scale_load(15)=15*1024 * on an 8-core system with 8 tasks each runnable on one CPU shares has * to be 15*1024*1/8=1920 instead of scale_load(MIN_SHARES)=2*1024. In * case no task is runnable on a CPU MIN_SHARES=2 should be returned * instead of 0. */ return clamp_t(long, shares, MIN_SHARES, tg_shares); } #endif /* CONFIG_SMP */ /* * Recomputes the group entity based on the current state of its group * runqueue. */ static void update_cfs_group(struct sched_entity *se) { struct cfs_rq *gcfs_rq = group_cfs_rq(se); long shares; if (!gcfs_rq) return; if (throttled_hierarchy(gcfs_rq)) return; #ifndef CONFIG_SMP shares = READ_ONCE(gcfs_rq->tg->shares); #else shares = calc_group_shares(gcfs_rq); #endif if (unlikely(se->load.weight != shares)) reweight_entity(cfs_rq_of(se), se, shares); } #else /* CONFIG_FAIR_GROUP_SCHED */ static inline void update_cfs_group(struct sched_entity *se) { } #endif /* CONFIG_FAIR_GROUP_SCHED */ static inline void cfs_rq_util_change(struct cfs_rq *cfs_rq, int flags) { struct rq *rq = rq_of(cfs_rq); if (&rq->cfs == cfs_rq) { /* * There are a few boundary cases this might miss but it should * get called often enough that that should (hopefully) not be * a real problem. * * It will not get called when we go idle, because the idle * thread is a different class (!fair), nor will the utilization * number include things like RT tasks. * * As is, the util number is not freq-invariant (we'd have to * implement arch_scale_freq_capacity() for that). * * See cpu_util_cfs(). */ cpufreq_update_util(rq, flags); } } #ifdef CONFIG_SMP static inline bool load_avg_is_decayed(struct sched_avg *sa) { if (sa->load_sum) return false; if (sa->util_sum) return false; if (sa->runnable_sum) return false; /* * _avg must be null when _sum are null because _avg = _sum / divider * Make sure that rounding and/or propagation of PELT values never * break this. */ SCHED_WARN_ON(sa->load_avg || sa->util_avg || sa->runnable_avg); return true; } static inline u64 cfs_rq_last_update_time(struct cfs_rq *cfs_rq) { return u64_u32_load_copy(cfs_rq->avg.last_update_time, cfs_rq->last_update_time_copy); } #ifdef CONFIG_FAIR_GROUP_SCHED /* * Because list_add_leaf_cfs_rq always places a child cfs_rq on the list * immediately before a parent cfs_rq, and cfs_rqs are removed from the list * bottom-up, we only have to test whether the cfs_rq before us on the list * is our child. * If cfs_rq is not on the list, test whether a child needs its to be added to * connect a branch to the tree * (see list_add_leaf_cfs_rq() for details). */ static inline bool child_cfs_rq_on_list(struct cfs_rq *cfs_rq) { struct cfs_rq *prev_cfs_rq; struct list_head *prev; if (cfs_rq->on_list) { prev = cfs_rq->leaf_cfs_rq_list.prev; } else { struct rq *rq = rq_of(cfs_rq); prev = rq->tmp_alone_branch; } prev_cfs_rq = container_of(prev, struct cfs_rq, leaf_cfs_rq_list); return (prev_cfs_rq->tg->parent == cfs_rq->tg); } static inline bool cfs_rq_is_decayed(struct cfs_rq *cfs_rq) { if (cfs_rq->load.weight) return false; if (!load_avg_is_decayed(&cfs_rq->avg)) return false; if (child_cfs_rq_on_list(cfs_rq)) return false; return true; } /** * update_tg_load_avg - update the tg's load avg * @cfs_rq: the cfs_rq whose avg changed * * This function 'ensures': tg->load_avg := \Sum tg->cfs_rq[]->avg.load. * However, because tg->load_avg is a global value there are performance * considerations. * * In order to avoid having to look at the other cfs_rq's, we use a * differential update where we store the last value we propagated. This in * turn allows skipping updates if the differential is 'small'. * * Updating tg's load_avg is necessary before update_cfs_share(). */ static inline void update_tg_load_avg(struct cfs_rq *cfs_rq) { long delta; u64 now; /* * No need to update load_avg for root_task_group as it is not used. */ if (cfs_rq->tg == &root_task_group) return; /* * For migration heavy workloads, access to tg->load_avg can be * unbound. Limit the update rate to at most once per ms. */ now = sched_clock_cpu(cpu_of(rq_of(cfs_rq))); if (now - cfs_rq->last_update_tg_load_avg < NSEC_PER_MSEC) return; delta = cfs_rq->avg.load_avg - cfs_rq->tg_load_avg_contrib; if (abs(delta) > cfs_rq->tg_load_avg_contrib / 64) { atomic_long_add(delta, &cfs_rq->tg->load_avg); cfs_rq->tg_load_avg_contrib = cfs_rq->avg.load_avg; cfs_rq->last_update_tg_load_avg = now; } } /* * Called within set_task_rq() right before setting a task's CPU. The * caller only guarantees p->pi_lock is held; no other assumptions, * including the state of rq->lock, should be made. */ void set_task_rq_fair(struct sched_entity *se, struct cfs_rq *prev, struct cfs_rq *next) { u64 p_last_update_time; u64 n_last_update_time; if (!sched_feat(ATTACH_AGE_LOAD)) return; /* * We are supposed to update the task to "current" time, then its up to * date and ready to go to new CPU/cfs_rq. But we have difficulty in * getting what current time is, so simply throw away the out-of-date * time. This will result in the wakee task is less decayed, but giving * the wakee more load sounds not bad. */ if (!(se->avg.last_update_time && prev)) return; p_last_update_time = cfs_rq_last_update_time(prev); n_last_update_time = cfs_rq_last_update_time(next); __update_load_avg_blocked_se(p_last_update_time, se); se->avg.last_update_time = n_last_update_time; } /* * When on migration a sched_entity joins/leaves the PELT hierarchy, we need to * propagate its contribution. The key to this propagation is the invariant * that for each group: * * ge->avg == grq->avg (1) * * _IFF_ we look at the pure running and runnable sums. Because they * represent the very same entity, just at different points in the hierarchy. * * Per the above update_tg_cfs_util() and update_tg_cfs_runnable() are trivial * and simply copies the running/runnable sum over (but still wrong, because * the group entity and group rq do not have their PELT windows aligned). * * However, update_tg_cfs_load() is more complex. So we have: * * ge->avg.load_avg = ge->load.weight * ge->avg.runnable_avg (2) * * And since, like util, the runnable part should be directly transferable, * the following would _appear_ to be the straight forward approach: * * grq->avg.load_avg = grq->load.weight * grq->avg.runnable_avg (3) * * And per (1) we have: * * ge->avg.runnable_avg == grq->avg.runnable_avg * * Which gives: * * ge->load.weight * grq->avg.load_avg * ge->avg.load_avg = ----------------------------------- (4) * grq->load.weight * * Except that is wrong! * * Because while for entities historical weight is not important and we * really only care about our future and therefore can consider a pure * runnable sum, runqueues can NOT do this. * * We specifically want runqueues to have a load_avg that includes * historical weights. Those represent the blocked load, the load we expect * to (shortly) return to us. This only works by keeping the weights as * integral part of the sum. We therefore cannot decompose as per (3). * * Another reason this doesn't work is that runnable isn't a 0-sum entity. * Imagine a rq with 2 tasks that each are runnable 2/3 of the time. Then the * rq itself is runnable anywhere between 2/3 and 1 depending on how the * runnable section of these tasks overlap (or not). If they were to perfectly * align the rq as a whole would be runnable 2/3 of the time. If however we * always have at least 1 runnable task, the rq as a whole is always runnable. * * So we'll have to approximate.. :/ * * Given the constraint: * * ge->avg.running_sum <= ge->avg.runnable_sum <= LOAD_AVG_MAX * * We can construct a rule that adds runnable to a rq by assuming minimal * overlap. * * On removal, we'll assume each task is equally runnable; which yields: * * grq->avg.runnable_sum = grq->avg.load_sum / grq->load.weight * * XXX: only do this for the part of runnable > running ? * */ static inline void update_tg_cfs_util(struct cfs_rq *cfs_rq, struct sched_entity *se, struct cfs_rq *gcfs_rq) { long delta_sum, delta_avg = gcfs_rq->avg.util_avg - se->avg.util_avg; u32 new_sum, divider; /* Nothing to update */ if (!delta_avg) return; /* * cfs_rq->avg.period_contrib can be used for both cfs_rq and se. * See ___update_load_avg() for details. */ divider = get_pelt_divider(&cfs_rq->avg); /* Set new sched_entity's utilization */ se->avg.util_avg = gcfs_rq->avg.util_avg; new_sum = se->avg.util_avg * divider; delta_sum = (long)new_sum - (long)se->avg.util_sum; se->avg.util_sum = new_sum; /* Update parent cfs_rq utilization */ add_positive(&cfs_rq->avg.util_avg, delta_avg); add_positive(&cfs_rq->avg.util_sum, delta_sum); /* See update_cfs_rq_load_avg() */ cfs_rq->avg.util_sum = max_t(u32, cfs_rq->avg.util_sum, cfs_rq->avg.util_avg * PELT_MIN_DIVIDER); } static inline void update_tg_cfs_runnable(struct cfs_rq *cfs_rq, struct sched_entity *se, struct cfs_rq *gcfs_rq) { long delta_sum, delta_avg = gcfs_rq->avg.runnable_avg - se->avg.runnable_avg; u32 new_sum, divider; /* Nothing to update */ if (!delta_avg) return; /* * cfs_rq->avg.period_contrib can be used for both cfs_rq and se. * See ___update_load_avg() for details. */ divider = get_pelt_divider(&cfs_rq->avg); /* Set new sched_entity's runnable */ se->avg.runnable_avg = gcfs_rq->avg.runnable_avg; new_sum = se->avg.runnable_avg * divider; delta_sum = (long)new_sum - (long)se->avg.runnable_sum; se->avg.runnable_sum = new_sum; /* Update parent cfs_rq runnable */ add_positive(&cfs_rq->avg.runnable_avg, delta_avg); add_positive(&cfs_rq->avg.runnable_sum, delta_sum); /* See update_cfs_rq_load_avg() */ cfs_rq->avg.runnable_sum = max_t(u32, cfs_rq->avg.runnable_sum, cfs_rq->avg.runnable_avg * PELT_MIN_DIVIDER); } static inline void update_tg_cfs_load(struct cfs_rq *cfs_rq, struct sched_entity *se, struct cfs_rq *gcfs_rq) { long delta_avg, running_sum, runnable_sum = gcfs_rq->prop_runnable_sum; unsigned long load_avg; u64 load_sum = 0; s64 delta_sum; u32 divider; if (!runnable_sum) return; gcfs_rq->prop_runnable_sum = 0; /* * cfs_rq->avg.period_contrib can be used for both cfs_rq and se. * See ___update_load_avg() for details. */ divider = get_pelt_divider(&cfs_rq->avg); if (runnable_sum >= 0) { /* * Add runnable; clip at LOAD_AVG_MAX. Reflects that until * the CPU is saturated running == runnable. */ runnable_sum += se->avg.load_sum; runnable_sum = min_t(long, runnable_sum, divider); } else { /* * Estimate the new unweighted runnable_sum of the gcfs_rq by * assuming all tasks are equally runnable. */ if (scale_load_down(gcfs_rq->load.weight)) { load_sum = div_u64(gcfs_rq->avg.load_sum, scale_load_down(gcfs_rq->load.weight)); } /* But make sure to not inflate se's runnable */ runnable_sum = min(se->avg.load_sum, load_sum); } /* * runnable_sum can't be lower than running_sum * Rescale running sum to be in the same range as runnable sum * running_sum is in [0 : LOAD_AVG_MAX << SCHED_CAPACITY_SHIFT] * runnable_sum is in [0 : LOAD_AVG_MAX] */ running_sum = se->avg.util_sum >> SCHED_CAPACITY_SHIFT; runnable_sum = max(runnable_sum, running_sum); load_sum = se_weight(se) * runnable_sum; load_avg = div_u64(load_sum, divider); delta_avg = load_avg - se->avg.load_avg; if (!delta_avg) return; delta_sum = load_sum - (s64)se_weight(se) * se->avg.load_sum; se->avg.load_sum = runnable_sum; se->avg.load_avg = load_avg; add_positive(&cfs_rq->avg.load_avg, delta_avg); add_positive(&cfs_rq->avg.load_sum, delta_sum); /* See update_cfs_rq_load_avg() */ cfs_rq->avg.load_sum = max_t(u32, cfs_rq->avg.load_sum, cfs_rq->avg.load_avg * PELT_MIN_DIVIDER); } static inline void add_tg_cfs_propagate(struct cfs_rq *cfs_rq, long runnable_sum) { cfs_rq->propagate = 1; cfs_rq->prop_runnable_sum += runnable_sum; } /* Update task and its cfs_rq load average */ static inline int propagate_entity_load_avg(struct sched_entity *se) { struct cfs_rq *cfs_rq, *gcfs_rq; if (entity_is_task(se)) return 0; gcfs_rq = group_cfs_rq(se); if (!gcfs_rq->propagate) return 0; gcfs_rq->propagate = 0; cfs_rq = cfs_rq_of(se); add_tg_cfs_propagate(cfs_rq, gcfs_rq->prop_runnable_sum); update_tg_cfs_util(cfs_rq, se, gcfs_rq); update_tg_cfs_runnable(cfs_rq, se, gcfs_rq); update_tg_cfs_load(cfs_rq, se, gcfs_rq); trace_pelt_cfs_tp(cfs_rq); trace_pelt_se_tp(se); return 1; } /* * Check if we need to update the load and the utilization of a blocked * group_entity: */ static inline bool skip_blocked_update(struct sched_entity *se) { struct cfs_rq *gcfs_rq = group_cfs_rq(se); /* * If sched_entity still have not zero load or utilization, we have to * decay it: */ if (se->avg.load_avg || se->avg.util_avg) return false; /* * If there is a pending propagation, we have to update the load and * the utilization of the sched_entity: */ if (gcfs_rq->propagate) return false; /* * Otherwise, the load and the utilization of the sched_entity is * already zero and there is no pending propagation, so it will be a * waste of time to try to decay it: */ return true; } #else /* CONFIG_FAIR_GROUP_SCHED */ static inline void update_tg_load_avg(struct cfs_rq *cfs_rq) {} static inline int propagate_entity_load_avg(struct sched_entity *se) { return 0; } static inline void add_tg_cfs_propagate(struct cfs_rq *cfs_rq, long runnable_sum) {} #endif /* CONFIG_FAIR_GROUP_SCHED */ #ifdef CONFIG_NO_HZ_COMMON static inline void migrate_se_pelt_lag(struct sched_entity *se) { u64 throttled = 0, now, lut; struct cfs_rq *cfs_rq; struct rq *rq; bool is_idle; if (load_avg_is_decayed(&se->avg)) return; cfs_rq = cfs_rq_of(se); rq = rq_of(cfs_rq); rcu_read_lock(); is_idle = is_idle_task(rcu_dereference(rq->curr)); rcu_read_unlock(); /* * The lag estimation comes with a cost we don't want to pay all the * time. Hence, limiting to the case where the source CPU is idle and * we know we are at the greatest risk to have an outdated clock. */ if (!is_idle) return; /* * Estimated "now" is: last_update_time + cfs_idle_lag + rq_idle_lag, where: * * last_update_time (the cfs_rq's last_update_time) * = cfs_rq_clock_pelt()@cfs_rq_idle * = rq_clock_pelt()@cfs_rq_idle * - cfs->throttled_clock_pelt_time@cfs_rq_idle * * cfs_idle_lag (delta between rq's update and cfs_rq's update) * = rq_clock_pelt()@rq_idle - rq_clock_pelt()@cfs_rq_idle * * rq_idle_lag (delta between now and rq's update) * = sched_clock_cpu() - rq_clock()@rq_idle * * We can then write: * * now = rq_clock_pelt()@rq_idle - cfs->throttled_clock_pelt_time + * sched_clock_cpu() - rq_clock()@rq_idle * Where: * rq_clock_pelt()@rq_idle is rq->clock_pelt_idle * rq_clock()@rq_idle is rq->clock_idle * cfs->throttled_clock_pelt_time@cfs_rq_idle * is cfs_rq->throttled_pelt_idle */ #ifdef CONFIG_CFS_BANDWIDTH throttled = u64_u32_load(cfs_rq->throttled_pelt_idle); /* The clock has been stopped for throttling */ if (throttled == U64_MAX) return; #endif now = u64_u32_load(rq->clock_pelt_idle); /* * Paired with _update_idle_rq_clock_pelt(). It ensures at the worst case * is observed the old clock_pelt_idle value and the new clock_idle, * which lead to an underestimation. The opposite would lead to an * overestimation. */ smp_rmb(); lut = cfs_rq_last_update_time(cfs_rq); now -= throttled; if (now < lut) /* * cfs_rq->avg.last_update_time is more recent than our * estimation, let's use it. */ now = lut; else now += sched_clock_cpu(cpu_of(rq)) - u64_u32_load(rq->clock_idle); __update_load_avg_blocked_se(now, se); } #else static void migrate_se_pelt_lag(struct sched_entity *se) {} #endif /** * update_cfs_rq_load_avg - update the cfs_rq's load/util averages * @now: current time, as per cfs_rq_clock_pelt() * @cfs_rq: cfs_rq to update * * The cfs_rq avg is the direct sum of all its entities (blocked and runnable) * avg. The immediate corollary is that all (fair) tasks must be attached. * * cfs_rq->avg is used for task_h_load() and update_cfs_share() for example. * * Return: true if the load decayed or we removed load. * * Since both these conditions indicate a changed cfs_rq->avg.load we should * call update_tg_load_avg() when this function returns true. */ static inline int update_cfs_rq_load_avg(u64 now, struct cfs_rq *cfs_rq) { unsigned long removed_load = 0, removed_util = 0, removed_runnable = 0; struct sched_avg *sa = &cfs_rq->avg; int decayed = 0; if (cfs_rq->removed.nr) { unsigned long r; u32 divider = get_pelt_divider(&cfs_rq->avg); raw_spin_lock(&cfs_rq->removed.lock); swap(cfs_rq->removed.util_avg, removed_util); swap(cfs_rq->removed.load_avg, removed_load); swap(cfs_rq->removed.runnable_avg, removed_runnable); cfs_rq->removed.nr = 0; raw_spin_unlock(&cfs_rq->removed.lock); r = removed_load; sub_positive(&sa->load_avg, r); sub_positive(&sa->load_sum, r * divider); /* See sa->util_sum below */ sa->load_sum = max_t(u32, sa->load_sum, sa->load_avg * PELT_MIN_DIVIDER); r = removed_util; sub_positive(&sa->util_avg, r); sub_positive(&sa->util_sum, r * divider); /* * Because of rounding, se->util_sum might ends up being +1 more than * cfs->util_sum. Although this is not a problem by itself, detaching * a lot of tasks with the rounding problem between 2 updates of * util_avg (~1ms) can make cfs->util_sum becoming null whereas * cfs_util_avg is not. * Check that util_sum is still above its lower bound for the new * util_avg. Given that period_contrib might have moved since the last * sync, we are only sure that util_sum must be above or equal to * util_avg * minimum possible divider */ sa->util_sum = max_t(u32, sa->util_sum, sa->util_avg * PELT_MIN_DIVIDER); r = removed_runnable; sub_positive(&sa->runnable_avg, r); sub_positive(&sa->runnable_sum, r * divider); /* See sa->util_sum above */ sa->runnable_sum = max_t(u32, sa->runnable_sum, sa->runnable_avg * PELT_MIN_DIVIDER); /* * removed_runnable is the unweighted version of removed_load so we * can use it to estimate removed_load_sum. */ add_tg_cfs_propagate(cfs_rq, -(long)(removed_runnable * divider) >> SCHED_CAPACITY_SHIFT); decayed = 1; } decayed |= __update_load_avg_cfs_rq(now, cfs_rq); u64_u32_store_copy(sa->last_update_time, cfs_rq->last_update_time_copy, sa->last_update_time); return decayed; } /** * attach_entity_load_avg - attach this entity to its cfs_rq load avg * @cfs_rq: cfs_rq to attach to * @se: sched_entity to attach * * Must call update_cfs_rq_load_avg() before this, since we rely on * cfs_rq->avg.last_update_time being current. */ static void attach_entity_load_avg(struct cfs_rq *cfs_rq, struct sched_entity *se) { /* * cfs_rq->avg.period_contrib can be used for both cfs_rq and se. * See ___update_load_avg() for details. */ u32 divider = get_pelt_divider(&cfs_rq->avg); /* * When we attach the @se to the @cfs_rq, we must align the decay * window because without that, really weird and wonderful things can * happen. * * XXX illustrate */ se->avg.last_update_time = cfs_rq->avg.last_update_time; se->avg.period_contrib = cfs_rq->avg.period_contrib; /* * Hell(o) Nasty stuff.. we need to recompute _sum based on the new * period_contrib. This isn't strictly correct, but since we're * entirely outside of the PELT hierarchy, nobody cares if we truncate * _sum a little. */ se->avg.util_sum = se->avg.util_avg * divider; se->avg.runnable_sum = se->avg.runnable_avg * divider; se->avg.load_sum = se->avg.load_avg * divider; if (se_weight(se) < se->avg.load_sum) se->avg.load_sum = div_u64(se->avg.load_sum, se_weight(se)); else se->avg.load_sum = 1; enqueue_load_avg(cfs_rq, se); cfs_rq->avg.util_avg += se->avg.util_avg; cfs_rq->avg.util_sum += se->avg.util_sum; cfs_rq->avg.runnable_avg += se->avg.runnable_avg; cfs_rq->avg.runnable_sum += se->avg.runnable_sum; add_tg_cfs_propagate(cfs_rq, se->avg.load_sum); cfs_rq_util_change(cfs_rq, 0); trace_pelt_cfs_tp(cfs_rq); } /** * detach_entity_load_avg - detach this entity from its cfs_rq load avg * @cfs_rq: cfs_rq to detach from * @se: sched_entity to detach * * Must call update_cfs_rq_load_avg() before this, since we rely on * cfs_rq->avg.last_update_time being current. */ static void detach_entity_load_avg(struct cfs_rq *cfs_rq, struct sched_entity *se) { dequeue_load_avg(cfs_rq, se); sub_positive(&cfs_rq->avg.util_avg, se->avg.util_avg); sub_positive(&cfs_rq->avg.util_sum, se->avg.util_sum); /* See update_cfs_rq_load_avg() */ cfs_rq->avg.util_sum = max_t(u32, cfs_rq->avg.util_sum, cfs_rq->avg.util_avg * PELT_MIN_DIVIDER); sub_positive(&cfs_rq->avg.runnable_avg, se->avg.runnable_avg); sub_positive(&cfs_rq->avg.runnable_sum, se->avg.runnable_sum); /* See update_cfs_rq_load_avg() */ cfs_rq->avg.runnable_sum = max_t(u32, cfs_rq->avg.runnable_sum, cfs_rq->avg.runnable_avg * PELT_MIN_DIVIDER); add_tg_cfs_propagate(cfs_rq, -se->avg.load_sum); cfs_rq_util_change(cfs_rq, 0); trace_pelt_cfs_tp(cfs_rq); } /* * Optional action to be done while updating the load average */ #define UPDATE_TG 0x1 #define SKIP_AGE_LOAD 0x2 #define DO_ATTACH 0x4 #define DO_DETACH 0x8 /* Update task and its cfs_rq load average */ static inline void update_load_avg(struct cfs_rq *cfs_rq, struct sched_entity *se, int flags) { u64 now = cfs_rq_clock_pelt(cfs_rq); int decayed; /* * Track task load average for carrying it to new CPU after migrated, and * track group sched_entity load average for task_h_load calc in migration */ if (se->avg.last_update_time && !(flags & SKIP_AGE_LOAD)) __update_load_avg_se(now, cfs_rq, se); decayed = update_cfs_rq_load_avg(now, cfs_rq); decayed |= propagate_entity_load_avg(se); if (!se->avg.last_update_time && (flags & DO_ATTACH)) { /* * DO_ATTACH means we're here from enqueue_entity(). * !last_update_time means we've passed through * migrate_task_rq_fair() indicating we migrated. * * IOW we're enqueueing a task on a new CPU. */ attach_entity_load_avg(cfs_rq, se); update_tg_load_avg(cfs_rq); } else if (flags & DO_DETACH) { /* * DO_DETACH means we're here from dequeue_entity() * and we are migrating task out of the CPU. */ detach_entity_load_avg(cfs_rq, se); update_tg_load_avg(cfs_rq); } else if (decayed) { cfs_rq_util_change(cfs_rq, 0); if (flags & UPDATE_TG) update_tg_load_avg(cfs_rq); } } /* * Synchronize entity load avg of dequeued entity without locking * the previous rq. */ static void sync_entity_load_avg(struct sched_entity *se) { struct cfs_rq *cfs_rq = cfs_rq_of(se); u64 last_update_time; last_update_time = cfs_rq_last_update_time(cfs_rq); __update_load_avg_blocked_se(last_update_time, se); } /* * Task first catches up with cfs_rq, and then subtract * itself from the cfs_rq (task must be off the queue now). */ static void remove_entity_load_avg(struct sched_entity *se) { struct cfs_rq *cfs_rq = cfs_rq_of(se); unsigned long flags; /* * tasks cannot exit without having gone through wake_up_new_task() -> * enqueue_task_fair() which will have added things to the cfs_rq, * so we can remove unconditionally. */ sync_entity_load_avg(se); raw_spin_lock_irqsave(&cfs_rq->removed.lock, flags); ++cfs_rq->removed.nr; cfs_rq->removed.util_avg += se->avg.util_avg; cfs_rq->removed.load_avg += se->avg.load_avg; cfs_rq->removed.runnable_avg += se->avg.runnable_avg; raw_spin_unlock_irqrestore(&cfs_rq->removed.lock, flags); } static inline unsigned long cfs_rq_runnable_avg(struct cfs_rq *cfs_rq) { return cfs_rq->avg.runnable_avg; } static inline unsigned long cfs_rq_load_avg(struct cfs_rq *cfs_rq) { return cfs_rq->avg.load_avg; } static int newidle_balance(struct rq *this_rq, struct rq_flags *rf); static inline unsigned long task_util(struct task_struct *p) { return READ_ONCE(p->se.avg.util_avg); } static inline unsigned long _task_util_est(struct task_struct *p) { struct util_est ue = READ_ONCE(p->se.avg.util_est); return max(ue.ewma, (ue.enqueued & ~UTIL_AVG_UNCHANGED)); } static inline unsigned long task_util_est(struct task_struct *p) { return max(task_util(p), _task_util_est(p)); } static inline void util_est_enqueue(struct cfs_rq *cfs_rq, struct task_struct *p) { unsigned int enqueued; if (!sched_feat(UTIL_EST)) return; /* Update root cfs_rq's estimated utilization */ enqueued = cfs_rq->avg.util_est.enqueued; enqueued += _task_util_est(p); WRITE_ONCE(cfs_rq->avg.util_est.enqueued, enqueued); trace_sched_util_est_cfs_tp(cfs_rq); } static inline void util_est_dequeue(struct cfs_rq *cfs_rq, struct task_struct *p) { unsigned int enqueued; if (!sched_feat(UTIL_EST)) return; /* Update root cfs_rq's estimated utilization */ enqueued = cfs_rq->avg.util_est.enqueued; enqueued -= min_t(unsigned int, enqueued, _task_util_est(p)); WRITE_ONCE(cfs_rq->avg.util_est.enqueued, enqueued); trace_sched_util_est_cfs_tp(cfs_rq); } #define UTIL_EST_MARGIN (SCHED_CAPACITY_SCALE / 100) /* * Check if a (signed) value is within a specified (unsigned) margin, * based on the observation that: * * abs(x) < y := (unsigned)(x + y - 1) < (2 * y - 1) * * NOTE: this only works when value + margin < INT_MAX. */ static inline bool within_margin(int value, int margin) { return ((unsigned int)(value + margin - 1) < (2 * margin - 1)); } static inline void util_est_update(struct cfs_rq *cfs_rq, struct task_struct *p, bool task_sleep) { long last_ewma_diff, last_enqueued_diff; struct util_est ue; if (!sched_feat(UTIL_EST)) return; /* * Skip update of task's estimated utilization when the task has not * yet completed an activation, e.g. being migrated. */ if (!task_sleep) return; /* * If the PELT values haven't changed since enqueue time, * skip the util_est update. */ ue = p->se.avg.util_est; if (ue.enqueued & UTIL_AVG_UNCHANGED) return; last_enqueued_diff = ue.enqueued; /* * Reset EWMA on utilization increases, the moving average is used only * to smooth utilization decreases. */ ue.enqueued = task_util(p); if (sched_feat(UTIL_EST_FASTUP)) { if (ue.ewma < ue.enqueued) { ue.ewma = ue.enqueued; goto done; } } /* * Skip update of task's estimated utilization when its members are * already ~1% close to its last activation value. */ last_ewma_diff = ue.enqueued - ue.ewma; last_enqueued_diff -= ue.enqueued; if (within_margin(last_ewma_diff, UTIL_EST_MARGIN)) { if (!within_margin(last_enqueued_diff, UTIL_EST_MARGIN)) goto done; return; } /* * To avoid overestimation of actual task utilization, skip updates if * we cannot grant there is idle time in this CPU. */ if (task_util(p) > arch_scale_cpu_capacity(cpu_of(rq_of(cfs_rq)))) return; /* * Update Task's estimated utilization * * When *p completes an activation we can consolidate another sample * of the task size. This is done by storing the current PELT value * as ue.enqueued and by using this value to update the Exponential * Weighted Moving Average (EWMA): * * ewma(t) = w * task_util(p) + (1-w) * ewma(t-1) * = w * task_util(p) + ewma(t-1) - w * ewma(t-1) * = w * (task_util(p) - ewma(t-1)) + ewma(t-1) * = w * ( last_ewma_diff ) + ewma(t-1) * = w * (last_ewma_diff + ewma(t-1) / w) * * Where 'w' is the weight of new samples, which is configured to be * 0.25, thus making w=1/4 ( >>= UTIL_EST_WEIGHT_SHIFT) */ ue.ewma <<= UTIL_EST_WEIGHT_SHIFT; ue.ewma += last_ewma_diff; ue.ewma >>= UTIL_EST_WEIGHT_SHIFT; done: ue.enqueued |= UTIL_AVG_UNCHANGED; WRITE_ONCE(p->se.avg.util_est, ue); trace_sched_util_est_se_tp(&p->se); } static inline int util_fits_cpu(unsigned long util, unsigned long uclamp_min, unsigned long uclamp_max, int cpu) { unsigned long capacity_orig, capacity_orig_thermal; unsigned long capacity = capacity_of(cpu); bool fits, uclamp_max_fits; /* * Check if the real util fits without any uclamp boost/cap applied. */ fits = fits_capacity(util, capacity); if (!uclamp_is_used()) return fits; /* * We must use arch_scale_cpu_capacity() for comparing against uclamp_min and * uclamp_max. We only care about capacity pressure (by using * capacity_of()) for comparing against the real util. * * If a task is boosted to 1024 for example, we don't want a tiny * pressure to skew the check whether it fits a CPU or not. * * Similarly if a task is capped to arch_scale_cpu_capacity(little_cpu), it * should fit a little cpu even if there's some pressure. * * Only exception is for thermal pressure since it has a direct impact * on available OPP of the system. * * We honour it for uclamp_min only as a drop in performance level * could result in not getting the requested minimum performance level. * * For uclamp_max, we can tolerate a drop in performance level as the * goal is to cap the task. So it's okay if it's getting less. */ capacity_orig = arch_scale_cpu_capacity(cpu); capacity_orig_thermal = capacity_orig - arch_scale_thermal_pressure(cpu); /* * We want to force a task to fit a cpu as implied by uclamp_max. * But we do have some corner cases to cater for.. * * * C=z * | ___ * | C=y | | * |_ _ _ _ _ _ _ _ _ ___ _ _ _ | _ | _ _ _ _ _ uclamp_max * | C=x | | | | * | ___ | | | | * | | | | | | | (util somewhere in this region) * | | | | | | | * | | | | | | | * +---------------------------------------- * cpu0 cpu1 cpu2 * * In the above example if a task is capped to a specific performance * point, y, then when: * * * util = 80% of x then it does not fit on cpu0 and should migrate * to cpu1 * * util = 80% of y then it is forced to fit on cpu1 to honour * uclamp_max request. * * which is what we're enforcing here. A task always fits if * uclamp_max <= capacity_orig. But when uclamp_max > capacity_orig, * the normal upmigration rules should withhold still. * * Only exception is when we are on max capacity, then we need to be * careful not to block overutilized state. This is so because: * * 1. There's no concept of capping at max_capacity! We can't go * beyond this performance level anyway. * 2. The system is being saturated when we're operating near * max capacity, it doesn't make sense to block overutilized. */ uclamp_max_fits = (capacity_orig == SCHED_CAPACITY_SCALE) && (uclamp_max == SCHED_CAPACITY_SCALE); uclamp_max_fits = !uclamp_max_fits && (uclamp_max <= capacity_orig); fits = fits || uclamp_max_fits; /* * * C=z * | ___ (region a, capped, util >= uclamp_max) * | C=y | | * |_ _ _ _ _ _ _ _ _ ___ _ _ _ | _ | _ _ _ _ _ uclamp_max * | C=x | | | | * | ___ | | | | (region b, uclamp_min <= util <= uclamp_max) * |_ _ _|_ _|_ _ _ _| _ | _ _ _| _ | _ _ _ _ _ uclamp_min * | | | | | | | * | | | | | | | (region c, boosted, util < uclamp_min) * +---------------------------------------- * cpu0 cpu1 cpu2 * * a) If util > uclamp_max, then we're capped, we don't care about * actual fitness value here. We only care if uclamp_max fits * capacity without taking margin/pressure into account. * See comment above. * * b) If uclamp_min <= util <= uclamp_max, then the normal * fits_capacity() rules apply. Except we need to ensure that we * enforce we remain within uclamp_max, see comment above. * * c) If util < uclamp_min, then we are boosted. Same as (b) but we * need to take into account the boosted value fits the CPU without * taking margin/pressure into account. * * Cases (a) and (b) are handled in the 'fits' variable already. We * just need to consider an extra check for case (c) after ensuring we * handle the case uclamp_min > uclamp_max. */ uclamp_min = min(uclamp_min, uclamp_max); if (fits && (util < uclamp_min) && (uclamp_min > capacity_orig_thermal)) return -1; return fits; } static inline int task_fits_cpu(struct task_struct *p, int cpu) { unsigned long uclamp_min = uclamp_eff_value(p, UCLAMP_MIN); unsigned long uclamp_max = uclamp_eff_value(p, UCLAMP_MAX); unsigned long util = task_util_est(p); /* * Return true only if the cpu fully fits the task requirements, which * include the utilization but also the performance hints. */ return (util_fits_cpu(util, uclamp_min, uclamp_max, cpu) > 0); } static inline void update_misfit_status(struct task_struct *p, struct rq *rq) { if (!sched_asym_cpucap_active()) return; if (!p || p->nr_cpus_allowed == 1) { rq->misfit_task_load = 0; return; } if (task_fits_cpu(p, cpu_of(rq))) { rq->misfit_task_load = 0; return; } /* * Make sure that misfit_task_load will not be null even if * task_h_load() returns 0. */ rq->misfit_task_load = max_t(unsigned long, task_h_load(p), 1); } #else /* CONFIG_SMP */ static inline bool cfs_rq_is_decayed(struct cfs_rq *cfs_rq) { return !cfs_rq->nr_running; } #define UPDATE_TG 0x0 #define SKIP_AGE_LOAD 0x0 #define DO_ATTACH 0x0 #define DO_DETACH 0x0 static inline void update_load_avg(struct cfs_rq *cfs_rq, struct sched_entity *se, int not_used1) { cfs_rq_util_change(cfs_rq, 0); } static inline void remove_entity_load_avg(struct sched_entity *se) {} static inline void attach_entity_load_avg(struct cfs_rq *cfs_rq, struct sched_entity *se) {} static inline void detach_entity_load_avg(struct cfs_rq *cfs_rq, struct sched_entity *se) {} static inline int newidle_balance(struct rq *rq, struct rq_flags *rf) { return 0; } static inline void util_est_enqueue(struct cfs_rq *cfs_rq, struct task_struct *p) {} static inline void util_est_dequeue(struct cfs_rq *cfs_rq, struct task_struct *p) {} static inline void util_est_update(struct cfs_rq *cfs_rq, struct task_struct *p, bool task_sleep) {} static inline void update_misfit_status(struct task_struct *p, struct rq *rq) {} #endif /* CONFIG_SMP */ static void place_entity(struct cfs_rq *cfs_rq, struct sched_entity *se, int flags) { u64 vslice, vruntime = avg_vruntime(cfs_rq); s64 lag = 0; se->slice = sysctl_sched_base_slice; vslice = calc_delta_fair(se->slice, se); /* * Due to how V is constructed as the weighted average of entities, * adding tasks with positive lag, or removing tasks with negative lag * will move 'time' backwards, this can screw around with the lag of * other tasks. * * EEVDF: placement strategy #1 / #2 */ if (sched_feat(PLACE_LAG) && cfs_rq->nr_running) { struct sched_entity *curr = cfs_rq->curr; unsigned long load; lag = se->vlag; /* * If we want to place a task and preserve lag, we have to * consider the effect of the new entity on the weighted * average and compensate for this, otherwise lag can quickly * evaporate. * * Lag is defined as: * * lag_i = S - s_i = w_i * (V - v_i) * * To avoid the 'w_i' term all over the place, we only track * the virtual lag: * * vl_i = V - v_i <=> v_i = V - vl_i * * And we take V to be the weighted average of all v: * * V = (\Sum w_j*v_j) / W * * Where W is: \Sum w_j * * Then, the weighted average after adding an entity with lag * vl_i is given by: * * V' = (\Sum w_j*v_j + w_i*v_i) / (W + w_i) * = (W*V + w_i*(V - vl_i)) / (W + w_i) * = (W*V + w_i*V - w_i*vl_i) / (W + w_i) * = (V*(W + w_i) - w_i*l) / (W + w_i) * = V - w_i*vl_i / (W + w_i) * * And the actual lag after adding an entity with vl_i is: * * vl'_i = V' - v_i * = V - w_i*vl_i / (W + w_i) - (V - vl_i) * = vl_i - w_i*vl_i / (W + w_i) * * Which is strictly less than vl_i. So in order to preserve lag * we should inflate the lag before placement such that the * effective lag after placement comes out right. * * As such, invert the above relation for vl'_i to get the vl_i * we need to use such that the lag after placement is the lag * we computed before dequeue. * * vl'_i = vl_i - w_i*vl_i / (W + w_i) * = ((W + w_i)*vl_i - w_i*vl_i) / (W + w_i) * * (W + w_i)*vl'_i = (W + w_i)*vl_i - w_i*vl_i * = W*vl_i * * vl_i = (W + w_i)*vl'_i / W */ load = cfs_rq->avg_load; if (curr && curr->on_rq) load += scale_load_down(curr->load.weight); lag *= load + scale_load_down(se->load.weight); if (WARN_ON_ONCE(!load)) load = 1; lag = div_s64(lag, load); } se->vruntime = vruntime - lag; /* * When joining the competition; the exisiting tasks will be, * on average, halfway through their slice, as such start tasks * off with half a slice to ease into the competition. */ if (sched_feat(PLACE_DEADLINE_INITIAL) && (flags & ENQUEUE_INITIAL)) vslice /= 2; /* * EEVDF: vd_i = ve_i + r_i/w_i */ se->deadline = se->vruntime + vslice; } static void check_enqueue_throttle(struct cfs_rq *cfs_rq); static inline int cfs_rq_throttled(struct cfs_rq *cfs_rq); static inline bool cfs_bandwidth_used(void); static void enqueue_entity(struct cfs_rq *cfs_rq, struct sched_entity *se, int flags) { bool curr = cfs_rq->curr == se; /* * If we're the current task, we must renormalise before calling * update_curr(). */ if (curr) place_entity(cfs_rq, se, flags); update_curr(cfs_rq); /* * When enqueuing a sched_entity, we must: * - Update loads to have both entity and cfs_rq synced with now. * - For group_entity, update its runnable_weight to reflect the new * h_nr_running of its group cfs_rq. * - For group_entity, update its weight to reflect the new share of * its group cfs_rq * - Add its new weight to cfs_rq->load.weight */ update_load_avg(cfs_rq, se, UPDATE_TG | DO_ATTACH); se_update_runnable(se); /* * XXX update_load_avg() above will have attached us to the pelt sum; * but update_cfs_group() here will re-adjust the weight and have to * undo/redo all that. Seems wasteful. */ update_cfs_group(se); /* * XXX now that the entity has been re-weighted, and it's lag adjusted, * we can place the entity. */ if (!curr) place_entity(cfs_rq, se, flags); account_entity_enqueue(cfs_rq, se); /* Entity has migrated, no longer consider this task hot */ if (flags & ENQUEUE_MIGRATED) se->exec_start = 0; check_schedstat_required(); update_stats_enqueue_fair(cfs_rq, se, flags); if (!curr) __enqueue_entity(cfs_rq, se); se->on_rq = 1; if (cfs_rq->nr_running == 1) { check_enqueue_throttle(cfs_rq); if (!throttled_hierarchy(cfs_rq)) { list_add_leaf_cfs_rq(cfs_rq); } else { #ifdef CONFIG_CFS_BANDWIDTH struct rq *rq = rq_of(cfs_rq); if (cfs_rq_throttled(cfs_rq) && !cfs_rq->throttled_clock) cfs_rq->throttled_clock = rq_clock(rq); if (!cfs_rq->throttled_clock_self) cfs_rq->throttled_clock_self = rq_clock(rq); #endif } } } static void __clear_buddies_next(struct sched_entity *se) { for_each_sched_entity(se) { struct cfs_rq *cfs_rq = cfs_rq_of(se); if (cfs_rq->next != se) break; cfs_rq->next = NULL; } } static void clear_buddies(struct cfs_rq *cfs_rq, struct sched_entity *se) { if (cfs_rq->next == se) __clear_buddies_next(se); } static __always_inline void return_cfs_rq_runtime(struct cfs_rq *cfs_rq); static void dequeue_entity(struct cfs_rq *cfs_rq, struct sched_entity *se, int flags) { int action = UPDATE_TG; if (entity_is_task(se) && task_on_rq_migrating(task_of(se))) action |= DO_DETACH; /* * Update run-time statistics of the 'current'. */ update_curr(cfs_rq); /* * When dequeuing a sched_entity, we must: * - Update loads to have both entity and cfs_rq synced with now. * - For group_entity, update its runnable_weight to reflect the new * h_nr_running of its group cfs_rq. * - Subtract its previous weight from cfs_rq->load.weight. * - For group entity, update its weight to reflect the new share * of its group cfs_rq. */ update_load_avg(cfs_rq, se, action); se_update_runnable(se); update_stats_dequeue_fair(cfs_rq, se, flags); clear_buddies(cfs_rq, se); update_entity_lag(cfs_rq, se); if (se != cfs_rq->curr) __dequeue_entity(cfs_rq, se); se->on_rq = 0; account_entity_dequeue(cfs_rq, se); /* return excess runtime on last dequeue */ return_cfs_rq_runtime(cfs_rq); update_cfs_group(se); /* * Now advance min_vruntime if @se was the entity holding it back, * except when: DEQUEUE_SAVE && !DEQUEUE_MOVE, in this case we'll be * put back on, and if we advance min_vruntime, we'll be placed back * further than we started -- ie. we'll be penalized. */ if ((flags & (DEQUEUE_SAVE | DEQUEUE_MOVE)) != DEQUEUE_SAVE) update_min_vruntime(cfs_rq); if (cfs_rq->nr_running == 0) update_idle_cfs_rq_clock_pelt(cfs_rq); } static void set_next_entity(struct cfs_rq *cfs_rq, struct sched_entity *se) { clear_buddies(cfs_rq, se); /* 'current' is not kept within the tree. */ if (se->on_rq) { /* * Any task has to be enqueued before it get to execute on * a CPU. So account for the time it spent waiting on the * runqueue. */ update_stats_wait_end_fair(cfs_rq, se); __dequeue_entity(cfs_rq, se); update_load_avg(cfs_rq, se, UPDATE_TG); /* * HACK, stash a copy of deadline at the point of pick in vlag, * which isn't used until dequeue. */ se->vlag = se->deadline; } update_stats_curr_start(cfs_rq, se); cfs_rq->curr = se; /* * Track our maximum slice length, if the CPU's load is at * least twice that of our own weight (i.e. dont track it * when there are only lesser-weight tasks around): */ if (schedstat_enabled() && rq_of(cfs_rq)->cfs.load.weight >= 2*se->load.weight) { struct sched_statistics *stats; stats = __schedstats_from_se(se); __schedstat_set(stats->slice_max, max((u64)stats->slice_max, se->sum_exec_runtime - se->prev_sum_exec_runtime)); } se->prev_sum_exec_runtime = se->sum_exec_runtime; } /* * Pick the next process, keeping these things in mind, in this order: * 1) keep things fair between processes/task groups * 2) pick the "next" process, since someone really wants that to run * 3) pick the "last" process, for cache locality * 4) do not run the "skip" process, if something else is available */ static struct sched_entity * pick_next_entity(struct cfs_rq *cfs_rq) { /* * Enabling NEXT_BUDDY will affect latency but not fairness. */ if (sched_feat(NEXT_BUDDY) && cfs_rq->next && entity_eligible(cfs_rq, cfs_rq->next)) return cfs_rq->next; return pick_eevdf(cfs_rq); } static bool check_cfs_rq_runtime(struct cfs_rq *cfs_rq); static void put_prev_entity(struct cfs_rq *cfs_rq, struct sched_entity *prev) { /* * If still on the runqueue then deactivate_task() * was not called and update_curr() has to be done: */ if (prev->on_rq) update_curr(cfs_rq); /* throttle cfs_rqs exceeding runtime */ check_cfs_rq_runtime(cfs_rq); if (prev->on_rq) { update_stats_wait_start_fair(cfs_rq, prev); /* Put 'current' back into the tree. */ __enqueue_entity(cfs_rq, prev); /* in !on_rq case, update occurred at dequeue */ update_load_avg(cfs_rq, prev, 0); } cfs_rq->curr = NULL; } static void entity_tick(struct cfs_rq *cfs_rq, struct sched_entity *curr, int queued) { /* * Update run-time statistics of the 'current'. */ update_curr(cfs_rq); /* * Ensure that runnable average is periodically updated. */ update_load_avg(cfs_rq, curr, UPDATE_TG); update_cfs_group(curr); #ifdef CONFIG_SCHED_HRTICK /* * queued ticks are scheduled to match the slice, so don't bother * validating it and just reschedule. */ if (queued) { resched_curr(rq_of(cfs_rq)); return; } /* * don't let the period tick interfere with the hrtick preemption */ if (!sched_feat(DOUBLE_TICK) && hrtimer_active(&rq_of(cfs_rq)->hrtick_timer)) return; #endif } /************************************************** * CFS bandwidth control machinery */ #ifdef CONFIG_CFS_BANDWIDTH #ifdef CONFIG_JUMP_LABEL static struct static_key __cfs_bandwidth_used; static inline bool cfs_bandwidth_used(void) { return static_key_false(&__cfs_bandwidth_used); } void cfs_bandwidth_usage_inc(void) { static_key_slow_inc_cpuslocked(&__cfs_bandwidth_used); } void cfs_bandwidth_usage_dec(void) { static_key_slow_dec_cpuslocked(&__cfs_bandwidth_used); } #else /* CONFIG_JUMP_LABEL */ static bool cfs_bandwidth_used(void) { return true; } void cfs_bandwidth_usage_inc(void) {} void cfs_bandwidth_usage_dec(void) {} #endif /* CONFIG_JUMP_LABEL */ /* * default period for cfs group bandwidth. * default: 0.1s, units: nanoseconds */ static inline u64 default_cfs_period(void) { return 100000000ULL; } static inline u64 sched_cfs_bandwidth_slice(void) { return (u64)sysctl_sched_cfs_bandwidth_slice * NSEC_PER_USEC; } /* * Replenish runtime according to assigned quota. We use sched_clock_cpu * directly instead of rq->clock to avoid adding additional synchronization * around rq->lock. * * requires cfs_b->lock */ void __refill_cfs_bandwidth_runtime(struct cfs_bandwidth *cfs_b) { s64 runtime; if (unlikely(cfs_b->quota == RUNTIME_INF)) return; cfs_b->runtime += cfs_b->quota; runtime = cfs_b->runtime_snap - cfs_b->runtime; if (runtime > 0) { cfs_b->burst_time += runtime; cfs_b->nr_burst++; } cfs_b->runtime = min(cfs_b->runtime, cfs_b->quota + cfs_b->burst); cfs_b->runtime_snap = cfs_b->runtime; } static inline struct cfs_bandwidth *tg_cfs_bandwidth(struct task_group *tg) { return &tg->cfs_bandwidth; } /* returns 0 on failure to allocate runtime */ static int __assign_cfs_rq_runtime(struct cfs_bandwidth *cfs_b, struct cfs_rq *cfs_rq, u64 target_runtime) { u64 min_amount, amount = 0; lockdep_assert_held(&cfs_b->lock); /* note: this is a positive sum as runtime_remaining <= 0 */ min_amount = target_runtime - cfs_rq->runtime_remaining; if (cfs_b->quota == RUNTIME_INF) amount = min_amount; else { start_cfs_bandwidth(cfs_b); if (cfs_b->runtime > 0) { amount = min(cfs_b->runtime, min_amount); cfs_b->runtime -= amount; cfs_b->idle = 0; } } cfs_rq->runtime_remaining += amount; return cfs_rq->runtime_remaining > 0; } /* returns 0 on failure to allocate runtime */ static int assign_cfs_rq_runtime(struct cfs_rq *cfs_rq) { struct cfs_bandwidth *cfs_b = tg_cfs_bandwidth(cfs_rq->tg); int ret; raw_spin_lock(&cfs_b->lock); ret = __assign_cfs_rq_runtime(cfs_b, cfs_rq, sched_cfs_bandwidth_slice()); raw_spin_unlock(&cfs_b->lock); return ret; } static void __account_cfs_rq_runtime(struct cfs_rq *cfs_rq, u64 delta_exec) { /* dock delta_exec before expiring quota (as it could span periods) */ cfs_rq->runtime_remaining -= delta_exec; if (likely(cfs_rq->runtime_remaining > 0)) return; if (cfs_rq->throttled) return; /* * if we're unable to extend our runtime we resched so that the active * hierarchy can be throttled */ if (!assign_cfs_rq_runtime(cfs_rq) && likely(cfs_rq->curr)) resched_curr(rq_of(cfs_rq)); } static __always_inline void account_cfs_rq_runtime(struct cfs_rq *cfs_rq, u64 delta_exec) { if (!cfs_bandwidth_used() || !cfs_rq->runtime_enabled) return; __account_cfs_rq_runtime(cfs_rq, delta_exec); } static inline int cfs_rq_throttled(struct cfs_rq *cfs_rq) { return cfs_bandwidth_used() && cfs_rq->throttled; } /* check whether cfs_rq, or any parent, is throttled */ static inline int throttled_hierarchy(struct cfs_rq *cfs_rq) { return cfs_bandwidth_used() && cfs_rq->throttle_count; } /* * Ensure that neither of the group entities corresponding to src_cpu or * dest_cpu are members of a throttled hierarchy when performing group * load-balance operations. */ static inline int throttled_lb_pair(struct task_group *tg, int src_cpu, int dest_cpu) { struct cfs_rq *src_cfs_rq, *dest_cfs_rq; src_cfs_rq = tg->cfs_rq[src_cpu]; dest_cfs_rq = tg->cfs_rq[dest_cpu]; return throttled_hierarchy(src_cfs_rq) || throttled_hierarchy(dest_cfs_rq); } static int tg_unthrottle_up(struct task_group *tg, void *data) { struct rq *rq = data; struct cfs_rq *cfs_rq = tg->cfs_rq[cpu_of(rq)]; cfs_rq->throttle_count--; if (!cfs_rq->throttle_count) { cfs_rq->throttled_clock_pelt_time += rq_clock_pelt(rq) - cfs_rq->throttled_clock_pelt; /* Add cfs_rq with load or one or more already running entities to the list */ if (!cfs_rq_is_decayed(cfs_rq)) list_add_leaf_cfs_rq(cfs_rq); if (cfs_rq->throttled_clock_self) { u64 delta = rq_clock(rq) - cfs_rq->throttled_clock_self; cfs_rq->throttled_clock_self = 0; if (SCHED_WARN_ON((s64)delta < 0)) delta = 0; cfs_rq->throttled_clock_self_time += delta; } } return 0; } static int tg_throttle_down(struct task_group *tg, void *data) { struct rq *rq = data; struct cfs_rq *cfs_rq = tg->cfs_rq[cpu_of(rq)]; /* group is entering throttled state, stop time */ if (!cfs_rq->throttle_count) { cfs_rq->throttled_clock_pelt = rq_clock_pelt(rq); list_del_leaf_cfs_rq(cfs_rq); SCHED_WARN_ON(cfs_rq->throttled_clock_self); if (cfs_rq->nr_running) cfs_rq->throttled_clock_self = rq_clock(rq); } cfs_rq->throttle_count++; return 0; } static bool throttle_cfs_rq(struct cfs_rq *cfs_rq) { struct rq *rq = rq_of(cfs_rq); struct cfs_bandwidth *cfs_b = tg_cfs_bandwidth(cfs_rq->tg); struct sched_entity *se; long task_delta, idle_task_delta, dequeue = 1; raw_spin_lock(&cfs_b->lock); /* This will start the period timer if necessary */ if (__assign_cfs_rq_runtime(cfs_b, cfs_rq, 1)) { /* * We have raced with bandwidth becoming available, and if we * actually throttled the timer might not unthrottle us for an * entire period. We additionally needed to make sure that any * subsequent check_cfs_rq_runtime calls agree not to throttle * us, as we may commit to do cfs put_prev+pick_next, so we ask * for 1ns of runtime rather than just check cfs_b. */ dequeue = 0; } else { list_add_tail_rcu(&cfs_rq->throttled_list, &cfs_b->throttled_cfs_rq); } raw_spin_unlock(&cfs_b->lock); if (!dequeue) return false; /* Throttle no longer required. */ se = cfs_rq->tg->se[cpu_of(rq_of(cfs_rq))]; /* freeze hierarchy runnable averages while throttled */ rcu_read_lock(); walk_tg_tree_from(cfs_rq->tg, tg_throttle_down, tg_nop, (void *)rq); rcu_read_unlock(); task_delta = cfs_rq->h_nr_running; idle_task_delta = cfs_rq->idle_h_nr_running; for_each_sched_entity(se) { struct cfs_rq *qcfs_rq = cfs_rq_of(se); /* throttled entity or throttle-on-deactivate */ if (!se->on_rq) goto done; dequeue_entity(qcfs_rq, se, DEQUEUE_SLEEP); if (cfs_rq_is_idle(group_cfs_rq(se))) idle_task_delta = cfs_rq->h_nr_running; qcfs_rq->h_nr_running -= task_delta; qcfs_rq->idle_h_nr_running -= idle_task_delta; if (qcfs_rq->load.weight) { /* Avoid re-evaluating load for this entity: */ se = parent_entity(se); break; } } for_each_sched_entity(se) { struct cfs_rq *qcfs_rq = cfs_rq_of(se); /* throttled entity or throttle-on-deactivate */ if (!se->on_rq) goto done; update_load_avg(qcfs_rq, se, 0); se_update_runnable(se); if (cfs_rq_is_idle(group_cfs_rq(se))) idle_task_delta = cfs_rq->h_nr_running; qcfs_rq->h_nr_running -= task_delta; qcfs_rq->idle_h_nr_running -= idle_task_delta; } /* At this point se is NULL and we are at root level*/ sub_nr_running(rq, task_delta); done: /* * Note: distribution will already see us throttled via the * throttled-list. rq->lock protects completion. */ cfs_rq->throttled = 1; SCHED_WARN_ON(cfs_rq->throttled_clock); if (cfs_rq->nr_running) cfs_rq->throttled_clock = rq_clock(rq); return true; } void unthrottle_cfs_rq(struct cfs_rq *cfs_rq) { struct rq *rq = rq_of(cfs_rq); struct cfs_bandwidth *cfs_b = tg_cfs_bandwidth(cfs_rq->tg); struct sched_entity *se; long task_delta, idle_task_delta; se = cfs_rq->tg->se[cpu_of(rq)]; cfs_rq->throttled = 0; update_rq_clock(rq); raw_spin_lock(&cfs_b->lock); if (cfs_rq->throttled_clock) { cfs_b->throttled_time += rq_clock(rq) - cfs_rq->throttled_clock; cfs_rq->throttled_clock = 0; } list_del_rcu(&cfs_rq->throttled_list); raw_spin_unlock(&cfs_b->lock); /* update hierarchical throttle state */ walk_tg_tree_from(cfs_rq->tg, tg_nop, tg_unthrottle_up, (void *)rq); if (!cfs_rq->load.weight) { if (!cfs_rq->on_list) return; /* * Nothing to run but something to decay (on_list)? * Complete the branch. */ for_each_sched_entity(se) { if (list_add_leaf_cfs_rq(cfs_rq_of(se))) break; } goto unthrottle_throttle; } task_delta = cfs_rq->h_nr_running; idle_task_delta = cfs_rq->idle_h_nr_running; for_each_sched_entity(se) { struct cfs_rq *qcfs_rq = cfs_rq_of(se); if (se->on_rq) break; enqueue_entity(qcfs_rq, se, ENQUEUE_WAKEUP); if (cfs_rq_is_idle(group_cfs_rq(se))) idle_task_delta = cfs_rq->h_nr_running; qcfs_rq->h_nr_running += task_delta; qcfs_rq->idle_h_nr_running += idle_task_delta; /* end evaluation on encountering a throttled cfs_rq */ if (cfs_rq_throttled(qcfs_rq)) goto unthrottle_throttle; } for_each_sched_entity(se) { struct cfs_rq *qcfs_rq = cfs_rq_of(se); update_load_avg(qcfs_rq, se, UPDATE_TG); se_update_runnable(se); if (cfs_rq_is_idle(group_cfs_rq(se))) idle_task_delta = cfs_rq->h_nr_running; qcfs_rq->h_nr_running += task_delta; qcfs_rq->idle_h_nr_running += idle_task_delta; /* end evaluation on encountering a throttled cfs_rq */ if (cfs_rq_throttled(qcfs_rq)) goto unthrottle_throttle; } /* At this point se is NULL and we are at root level*/ add_nr_running(rq, task_delta); unthrottle_throttle: assert_list_leaf_cfs_rq(rq); /* Determine whether we need to wake up potentially idle CPU: */ if (rq->curr == rq->idle && rq->cfs.nr_running) resched_curr(rq); } #ifdef CONFIG_SMP static void __cfsb_csd_unthrottle(void *arg) { struct cfs_rq *cursor, *tmp; struct rq *rq = arg; struct rq_flags rf; rq_lock(rq, &rf); /* * Iterating over the list can trigger several call to * update_rq_clock() in unthrottle_cfs_rq(). * Do it once and skip the potential next ones. */ update_rq_clock(rq); rq_clock_start_loop_update(rq); /* * Since we hold rq lock we're safe from concurrent manipulation of * the CSD list. However, this RCU critical section annotates the * fact that we pair with sched_free_group_rcu(), so that we cannot * race with group being freed in the window between removing it * from the list and advancing to the next entry in the list. */ rcu_read_lock(); list_for_each_entry_safe(cursor, tmp, &rq->cfsb_csd_list, throttled_csd_list) { list_del_init(&cursor->throttled_csd_list); if (cfs_rq_throttled(cursor)) unthrottle_cfs_rq(cursor); } rcu_read_unlock(); rq_clock_stop_loop_update(rq); rq_unlock(rq, &rf); } static inline void __unthrottle_cfs_rq_async(struct cfs_rq *cfs_rq) { struct rq *rq = rq_of(cfs_rq); bool first; if (rq == this_rq()) { unthrottle_cfs_rq(cfs_rq); return; } /* Already enqueued */ if (SCHED_WARN_ON(!list_empty(&cfs_rq->throttled_csd_list))) return; first = list_empty(&rq->cfsb_csd_list); list_add_tail(&cfs_rq->throttled_csd_list, &rq->cfsb_csd_list); if (first) smp_call_function_single_async(cpu_of(rq), &rq->cfsb_csd); } #else static inline void __unthrottle_cfs_rq_async(struct cfs_rq *cfs_rq) { unthrottle_cfs_rq(cfs_rq); } #endif static void unthrottle_cfs_rq_async(struct cfs_rq *cfs_rq) { lockdep_assert_rq_held(rq_of(cfs_rq)); if (SCHED_WARN_ON(!cfs_rq_throttled(cfs_rq) || cfs_rq->runtime_remaining <= 0)) return; __unthrottle_cfs_rq_async(cfs_rq); } static bool distribute_cfs_runtime(struct cfs_bandwidth *cfs_b) { int this_cpu = smp_processor_id(); u64 runtime, remaining = 1; bool throttled = false; struct cfs_rq *cfs_rq, *tmp; struct rq_flags rf; struct rq *rq; LIST_HEAD(local_unthrottle); rcu_read_lock(); list_for_each_entry_rcu(cfs_rq, &cfs_b->throttled_cfs_rq, throttled_list) { rq = rq_of(cfs_rq); if (!remaining) { throttled = true; break; } rq_lock_irqsave(rq, &rf); if (!cfs_rq_throttled(cfs_rq)) goto next; /* Already queued for async unthrottle */ if (!list_empty(&cfs_rq->throttled_csd_list)) goto next; /* By the above checks, this should never be true */ SCHED_WARN_ON(cfs_rq->runtime_remaining > 0); raw_spin_lock(&cfs_b->lock); runtime = -cfs_rq->runtime_remaining + 1; if (runtime > cfs_b->runtime) runtime = cfs_b->runtime; cfs_b->runtime -= runtime; remaining = cfs_b->runtime; raw_spin_unlock(&cfs_b->lock); cfs_rq->runtime_remaining += runtime; /* we check whether we're throttled above */ if (cfs_rq->runtime_remaining > 0) { if (cpu_of(rq) != this_cpu) { unthrottle_cfs_rq_async(cfs_rq); } else { /* * We currently only expect to be unthrottling * a single cfs_rq locally. */ SCHED_WARN_ON(!list_empty(&local_unthrottle)); list_add_tail(&cfs_rq->throttled_csd_list, &local_unthrottle); } } else { throttled = true; } next: rq_unlock_irqrestore(rq, &rf); } list_for_each_entry_safe(cfs_rq, tmp, &local_unthrottle, throttled_csd_list) { struct rq *rq = rq_of(cfs_rq); rq_lock_irqsave(rq, &rf); list_del_init(&cfs_rq->throttled_csd_list); if (cfs_rq_throttled(cfs_rq)) unthrottle_cfs_rq(cfs_rq); rq_unlock_irqrestore(rq, &rf); } SCHED_WARN_ON(!list_empty(&local_unthrottle)); rcu_read_unlock(); return throttled; } /* * Responsible for refilling a task_group's bandwidth and unthrottling its * cfs_rqs as appropriate. If there has been no activity within the last * period the timer is deactivated until scheduling resumes; cfs_b->idle is * used to track this state. */ static int do_sched_cfs_period_timer(struct cfs_bandwidth *cfs_b, int overrun, unsigned long flags) { int throttled; /* no need to continue the timer with no bandwidth constraint */ if (cfs_b->quota == RUNTIME_INF) goto out_deactivate; throttled = !list_empty(&cfs_b->throttled_cfs_rq); cfs_b->nr_periods += overrun; /* Refill extra burst quota even if cfs_b->idle */ __refill_cfs_bandwidth_runtime(cfs_b); /* * idle depends on !throttled (for the case of a large deficit), and if * we're going inactive then everything else can be deferred */ if (cfs_b->idle && !throttled) goto out_deactivate; if (!throttled) { /* mark as potentially idle for the upcoming period */ cfs_b->idle = 1; return 0; } /* account preceding periods in which throttling occurred */ cfs_b->nr_throttled += overrun; /* * This check is repeated as we release cfs_b->lock while we unthrottle. */ while (throttled && cfs_b->runtime > 0) { raw_spin_unlock_irqrestore(&cfs_b->lock, flags); /* we can't nest cfs_b->lock while distributing bandwidth */ throttled = distribute_cfs_runtime(cfs_b); raw_spin_lock_irqsave(&cfs_b->lock, flags); } /* * While we are ensured activity in the period following an * unthrottle, this also covers the case in which the new bandwidth is * insufficient to cover the existing bandwidth deficit. (Forcing the * timer to remain active while there are any throttled entities.) */ cfs_b->idle = 0; return 0; out_deactivate: return 1; } /* a cfs_rq won't donate quota below this amount */ static const u64 min_cfs_rq_runtime = 1 * NSEC_PER_MSEC; /* minimum remaining period time to redistribute slack quota */ static const u64 min_bandwidth_expiration = 2 * NSEC_PER_MSEC; /* how long we wait to gather additional slack before distributing */ static const u64 cfs_bandwidth_slack_period = 5 * NSEC_PER_MSEC; /* * Are we near the end of the current quota period? * * Requires cfs_b->lock for hrtimer_expires_remaining to be safe against the * hrtimer base being cleared by hrtimer_start. In the case of * migrate_hrtimers, base is never cleared, so we are fine. */ static int runtime_refresh_within(struct cfs_bandwidth *cfs_b, u64 min_expire) { struct hrtimer *refresh_timer = &cfs_b->period_timer; s64 remaining; /* if the call-back is running a quota refresh is already occurring */ if (hrtimer_callback_running(refresh_timer)) return 1; /* is a quota refresh about to occur? */ remaining = ktime_to_ns(hrtimer_expires_remaining(refresh_timer)); if (remaining < (s64)min_expire) return 1; return 0; } static void start_cfs_slack_bandwidth(struct cfs_bandwidth *cfs_b) { u64 min_left = cfs_bandwidth_slack_period + min_bandwidth_expiration; /* if there's a quota refresh soon don't bother with slack */ if (runtime_refresh_within(cfs_b, min_left)) return; /* don't push forwards an existing deferred unthrottle */ if (cfs_b->slack_started) return; cfs_b->slack_started = true; hrtimer_start(&cfs_b->slack_timer, ns_to_ktime(cfs_bandwidth_slack_period), HRTIMER_MODE_REL); } /* we know any runtime found here is valid as update_curr() precedes return */ static void __return_cfs_rq_runtime(struct cfs_rq *cfs_rq) { struct cfs_bandwidth *cfs_b = tg_cfs_bandwidth(cfs_rq->tg); s64 slack_runtime = cfs_rq->runtime_remaining - min_cfs_rq_runtime; if (slack_runtime <= 0) return; raw_spin_lock(&cfs_b->lock); if (cfs_b->quota != RUNTIME_INF) { cfs_b->runtime += slack_runtime; /* we are under rq->lock, defer unthrottling using a timer */ if (cfs_b->runtime > sched_cfs_bandwidth_slice() && !list_empty(&cfs_b->throttled_cfs_rq)) start_cfs_slack_bandwidth(cfs_b); } raw_spin_unlock(&cfs_b->lock); /* even if it's not valid for return we don't want to try again */ cfs_rq->runtime_remaining -= slack_runtime; } static __always_inline void return_cfs_rq_runtime(struct cfs_rq *cfs_rq) { if (!cfs_bandwidth_used()) return; if (!cfs_rq->runtime_enabled || cfs_rq->nr_running) return; __return_cfs_rq_runtime(cfs_rq); } /* * This is done with a timer (instead of inline with bandwidth return) since * it's necessary to juggle rq->locks to unthrottle their respective cfs_rqs. */ static void do_sched_cfs_slack_timer(struct cfs_bandwidth *cfs_b) { u64 runtime = 0, slice = sched_cfs_bandwidth_slice(); unsigned long flags; /* confirm we're still not at a refresh boundary */ raw_spin_lock_irqsave(&cfs_b->lock, flags); cfs_b->slack_started = false; if (runtime_refresh_within(cfs_b, min_bandwidth_expiration)) { raw_spin_unlock_irqrestore(&cfs_b->lock, flags); return; } if (cfs_b->quota != RUNTIME_INF && cfs_b->runtime > slice) runtime = cfs_b->runtime; raw_spin_unlock_irqrestore(&cfs_b->lock, flags); if (!runtime) return; distribute_cfs_runtime(cfs_b); } /* * When a group wakes up we want to make sure that its quota is not already * expired/exceeded, otherwise it may be allowed to steal additional ticks of * runtime as update_curr() throttling can not trigger until it's on-rq. */ static void check_enqueue_throttle(struct cfs_rq *cfs_rq) { if (!cfs_bandwidth_used()) return; /* an active group must be handled by the update_curr()->put() path */ if (!cfs_rq->runtime_enabled || cfs_rq->curr) return; /* ensure the group is not already throttled */ if (cfs_rq_throttled(cfs_rq)) return; /* update runtime allocation */ account_cfs_rq_runtime(cfs_rq, 0); if (cfs_rq->runtime_remaining <= 0) throttle_cfs_rq(cfs_rq); } static void sync_throttle(struct task_group *tg, int cpu) { struct cfs_rq *pcfs_rq, *cfs_rq; if (!cfs_bandwidth_used()) return; if (!tg->parent) return; cfs_rq = tg->cfs_rq[cpu]; pcfs_rq = tg->parent->cfs_rq[cpu]; cfs_rq->throttle_count = pcfs_rq->throttle_count; cfs_rq->throttled_clock_pelt = rq_clock_pelt(cpu_rq(cpu)); } /* conditionally throttle active cfs_rq's from put_prev_entity() */ static bool check_cfs_rq_runtime(struct cfs_rq *cfs_rq) { if (!cfs_bandwidth_used()) return false; if (likely(!cfs_rq->runtime_enabled || cfs_rq->runtime_remaining > 0)) return false; /* * it's possible for a throttled entity to be forced into a running * state (e.g. set_curr_task), in this case we're finished. */ if (cfs_rq_throttled(cfs_rq)) return true; return throttle_cfs_rq(cfs_rq); } static enum hrtimer_restart sched_cfs_slack_timer(struct hrtimer *timer) { struct cfs_bandwidth *cfs_b = container_of(timer, struct cfs_bandwidth, slack_timer); do_sched_cfs_slack_timer(cfs_b); return HRTIMER_NORESTART; } extern const u64 max_cfs_quota_period; static enum hrtimer_restart sched_cfs_period_timer(struct hrtimer *timer) { struct cfs_bandwidth *cfs_b = container_of(timer, struct cfs_bandwidth, period_timer); unsigned long flags; int overrun; int idle = 0; int count = 0; raw_spin_lock_irqsave(&cfs_b->lock, flags); for (;;) { overrun = hrtimer_forward_now(timer, cfs_b->period); if (!overrun) break; idle = do_sched_cfs_period_timer(cfs_b, overrun, flags); if (++count > 3) { u64 new, old = ktime_to_ns(cfs_b->period); /* * Grow period by a factor of 2 to avoid losing precision. * Precision loss in the quota/period ratio can cause __cfs_schedulable * to fail. */ new = old * 2; if (new < max_cfs_quota_period) { cfs_b->period = ns_to_ktime(new); cfs_b->quota *= 2; cfs_b->burst *= 2; pr_warn_ratelimited( "cfs_period_timer[cpu%d]: period too short, scaling up (new cfs_period_us = %lld, cfs_quota_us = %lld)\n", smp_processor_id(), div_u64(new, NSEC_PER_USEC), div_u64(cfs_b->quota, NSEC_PER_USEC)); } else { pr_warn_ratelimited( "cfs_period_timer[cpu%d]: period too short, but cannot scale up without losing precision (cfs_period_us = %lld, cfs_quota_us = %lld)\n", smp_processor_id(), div_u64(old, NSEC_PER_USEC), div_u64(cfs_b->quota, NSEC_PER_USEC)); } /* reset count so we don't come right back in here */ count = 0; } } if (idle) cfs_b->period_active = 0; raw_spin_unlock_irqrestore(&cfs_b->lock, flags); return idle ? HRTIMER_NORESTART : HRTIMER_RESTART; } void init_cfs_bandwidth(struct cfs_bandwidth *cfs_b, struct cfs_bandwidth *parent) { raw_spin_lock_init(&cfs_b->lock); cfs_b->runtime = 0; cfs_b->quota = RUNTIME_INF; cfs_b->period = ns_to_ktime(default_cfs_period()); cfs_b->burst = 0; cfs_b->hierarchical_quota = parent ? parent->hierarchical_quota : RUNTIME_INF; INIT_LIST_HEAD(&cfs_b->throttled_cfs_rq); hrtimer_init(&cfs_b->period_timer, CLOCK_MONOTONIC, HRTIMER_MODE_ABS_PINNED); cfs_b->period_timer.function = sched_cfs_period_timer; /* Add a random offset so that timers interleave */ hrtimer_set_expires(&cfs_b->period_timer, get_random_u32_below(cfs_b->period)); hrtimer_init(&cfs_b->slack_timer, CLOCK_MONOTONIC, HRTIMER_MODE_REL); cfs_b->slack_timer.function = sched_cfs_slack_timer; cfs_b->slack_started = false; } static void init_cfs_rq_runtime(struct cfs_rq *cfs_rq) { cfs_rq->runtime_enabled = 0; INIT_LIST_HEAD(&cfs_rq->throttled_list); INIT_LIST_HEAD(&cfs_rq->throttled_csd_list); } void start_cfs_bandwidth(struct cfs_bandwidth *cfs_b) { lockdep_assert_held(&cfs_b->lock); if (cfs_b->period_active) return; cfs_b->period_active = 1; hrtimer_forward_now(&cfs_b->period_timer, cfs_b->period); hrtimer_start_expires(&cfs_b->period_timer, HRTIMER_MODE_ABS_PINNED); } static void destroy_cfs_bandwidth(struct cfs_bandwidth *cfs_b) { int __maybe_unused i; /* init_cfs_bandwidth() was not called */ if (!cfs_b->throttled_cfs_rq.next) return; hrtimer_cancel(&cfs_b->period_timer); hrtimer_cancel(&cfs_b->slack_timer); /* * It is possible that we still have some cfs_rq's pending on a CSD * list, though this race is very rare. In order for this to occur, we * must have raced with the last task leaving the group while there * exist throttled cfs_rq(s), and the period_timer must have queued the * CSD item but the remote cpu has not yet processed it. To handle this, * we can simply flush all pending CSD work inline here. We're * guaranteed at this point that no additional cfs_rq of this group can * join a CSD list. */ #ifdef CONFIG_SMP for_each_possible_cpu(i) { struct rq *rq = cpu_rq(i); unsigned long flags; if (list_empty(&rq->cfsb_csd_list)) continue; local_irq_save(flags); __cfsb_csd_unthrottle(rq); local_irq_restore(flags); } #endif } /* * Both these CPU hotplug callbacks race against unregister_fair_sched_group() * * The race is harmless, since modifying bandwidth settings of unhooked group * bits doesn't do much. */ /* cpu online callback */ static void __maybe_unused update_runtime_enabled(struct rq *rq) { struct task_group *tg; lockdep_assert_rq_held(rq); rcu_read_lock(); list_for_each_entry_rcu(tg, &task_groups, list) { struct cfs_bandwidth *cfs_b = &tg->cfs_bandwidth; struct cfs_rq *cfs_rq = tg->cfs_rq[cpu_of(rq)]; raw_spin_lock(&cfs_b->lock); cfs_rq->runtime_enabled = cfs_b->quota != RUNTIME_INF; raw_spin_unlock(&cfs_b->lock); } rcu_read_unlock(); } /* cpu offline callback */ static void __maybe_unused unthrottle_offline_cfs_rqs(struct rq *rq) { struct task_group *tg; lockdep_assert_rq_held(rq); /* * The rq clock has already been updated in the * set_rq_offline(), so we should skip updating * the rq clock again in unthrottle_cfs_rq(). */ rq_clock_start_loop_update(rq); rcu_read_lock(); list_for_each_entry_rcu(tg, &task_groups, list) { struct cfs_rq *cfs_rq = tg->cfs_rq[cpu_of(rq)]; if (!cfs_rq->runtime_enabled) continue; /* * clock_task is not advancing so we just need to make sure * there's some valid quota amount */ cfs_rq->runtime_remaining = 1; /* * Offline rq is schedulable till CPU is completely disabled * in take_cpu_down(), so we prevent new cfs throttling here. */ cfs_rq->runtime_enabled = 0; if (cfs_rq_throttled(cfs_rq)) unthrottle_cfs_rq(cfs_rq); } rcu_read_unlock(); rq_clock_stop_loop_update(rq); } bool cfs_task_bw_constrained(struct task_struct *p) { struct cfs_rq *cfs_rq = task_cfs_rq(p); if (!cfs_bandwidth_used()) return false; if (cfs_rq->runtime_enabled || tg_cfs_bandwidth(cfs_rq->tg)->hierarchical_quota != RUNTIME_INF) return true; return false; } #ifdef CONFIG_NO_HZ_FULL /* called from pick_next_task_fair() */ static void sched_fair_update_stop_tick(struct rq *rq, struct task_struct *p) { int cpu = cpu_of(rq); if (!sched_feat(HZ_BW) || !cfs_bandwidth_used()) return; if (!tick_nohz_full_cpu(cpu)) return; if (rq->nr_running != 1) return; /* * We know there is only one task runnable and we've just picked it. The * normal enqueue path will have cleared TICK_DEP_BIT_SCHED if we will * be otherwise able to stop the tick. Just need to check if we are using * bandwidth control. */ if (cfs_task_bw_constrained(p)) tick_nohz_dep_set_cpu(cpu, TICK_DEP_BIT_SCHED); } #endif #else /* CONFIG_CFS_BANDWIDTH */ static inline bool cfs_bandwidth_used(void) { return false; } static void account_cfs_rq_runtime(struct cfs_rq *cfs_rq, u64 delta_exec) {} static bool check_cfs_rq_runtime(struct cfs_rq *cfs_rq) { return false; } static void check_enqueue_throttle(struct cfs_rq *cfs_rq) {} static inline void sync_throttle(struct task_group *tg, int cpu) {} static __always_inline void return_cfs_rq_runtime(struct cfs_rq *cfs_rq) {} static inline int cfs_rq_throttled(struct cfs_rq *cfs_rq) { return 0; } static inline int throttled_hierarchy(struct cfs_rq *cfs_rq) { return 0; } static inline int throttled_lb_pair(struct task_group *tg, int src_cpu, int dest_cpu) { return 0; } #ifdef CONFIG_FAIR_GROUP_SCHED void init_cfs_bandwidth(struct cfs_bandwidth *cfs_b, struct cfs_bandwidth *parent) {} static void init_cfs_rq_runtime(struct cfs_rq *cfs_rq) {} #endif static inline struct cfs_bandwidth *tg_cfs_bandwidth(struct task_group *tg) { return NULL; } static inline void destroy_cfs_bandwidth(struct cfs_bandwidth *cfs_b) {} static inline void update_runtime_enabled(struct rq *rq) {} static inline void unthrottle_offline_cfs_rqs(struct rq *rq) {} #ifdef CONFIG_CGROUP_SCHED bool cfs_task_bw_constrained(struct task_struct *p) { return false; } #endif #endif /* CONFIG_CFS_BANDWIDTH */ #if !defined(CONFIG_CFS_BANDWIDTH) || !defined(CONFIG_NO_HZ_FULL) static inline void sched_fair_update_stop_tick(struct rq *rq, struct task_struct *p) {} #endif /************************************************** * CFS operations on tasks: */ #ifdef CONFIG_SCHED_HRTICK static void hrtick_start_fair(struct rq *rq, struct task_struct *p) { struct sched_entity *se = &p->se; SCHED_WARN_ON(task_rq(p) != rq); if (rq->cfs.h_nr_running > 1) { u64 ran = se->sum_exec_runtime - se->prev_sum_exec_runtime; u64 slice = se->slice; s64 delta = slice - ran; if (delta < 0) { if (task_current(rq, p)) resched_curr(rq); return; } hrtick_start(rq, delta); } } /* * called from enqueue/dequeue and updates the hrtick when the * current task is from our class and nr_running is low enough * to matter. */ static void hrtick_update(struct rq *rq) { struct task_struct *curr = rq->curr; if (!hrtick_enabled_fair(rq) || curr->sched_class != &fair_sched_class) return; hrtick_start_fair(rq, curr); } #else /* !CONFIG_SCHED_HRTICK */ static inline void hrtick_start_fair(struct rq *rq, struct task_struct *p) { } static inline void hrtick_update(struct rq *rq) { } #endif #ifdef CONFIG_SMP static inline bool cpu_overutilized(int cpu) { unsigned long rq_util_min = uclamp_rq_get(cpu_rq(cpu), UCLAMP_MIN); unsigned long rq_util_max = uclamp_rq_get(cpu_rq(cpu), UCLAMP_MAX); /* Return true only if the utilization doesn't fit CPU's capacity */ return !util_fits_cpu(cpu_util_cfs(cpu), rq_util_min, rq_util_max, cpu); } static inline void update_overutilized_status(struct rq *rq) { if (!READ_ONCE(rq->rd->overutilized) && cpu_overutilized(rq->cpu)) { WRITE_ONCE(rq->rd->overutilized, SG_OVERUTILIZED); trace_sched_overutilized_tp(rq->rd, SG_OVERUTILIZED); } } #else static inline void update_overutilized_status(struct rq *rq) { } #endif /* Runqueue only has SCHED_IDLE tasks enqueued */ static int sched_idle_rq(struct rq *rq) { return unlikely(rq->nr_running == rq->cfs.idle_h_nr_running && rq->nr_running); } #ifdef CONFIG_SMP static int sched_idle_cpu(int cpu) { return sched_idle_rq(cpu_rq(cpu)); } #endif /* * The enqueue_task method is called before nr_running is * increased. Here we update the fair scheduling stats and * then put the task into the rbtree: */ static void enqueue_task_fair(struct rq *rq, struct task_struct *p, int flags) { struct cfs_rq *cfs_rq; struct sched_entity *se = &p->se; int idle_h_nr_running = task_has_idle_policy(p); int task_new = !(flags & ENQUEUE_WAKEUP); /* * The code below (indirectly) updates schedutil which looks at * the cfs_rq utilization to select a frequency. * Let's add the task's estimated utilization to the cfs_rq's * estimated utilization, before we update schedutil. */ util_est_enqueue(&rq->cfs, p); /* * If in_iowait is set, the code below may not trigger any cpufreq * utilization updates, so do it here explicitly with the IOWAIT flag * passed. */ if (p->in_iowait) cpufreq_update_util(rq, SCHED_CPUFREQ_IOWAIT); for_each_sched_entity(se) { if (se->on_rq) break; cfs_rq = cfs_rq_of(se); enqueue_entity(cfs_rq, se, flags); cfs_rq->h_nr_running++; cfs_rq->idle_h_nr_running += idle_h_nr_running; if (cfs_rq_is_idle(cfs_rq)) idle_h_nr_running = 1; /* end evaluation on encountering a throttled cfs_rq */ if (cfs_rq_throttled(cfs_rq)) goto enqueue_throttle; flags = ENQUEUE_WAKEUP; } for_each_sched_entity(se) { cfs_rq = cfs_rq_of(se); update_load_avg(cfs_rq, se, UPDATE_TG); se_update_runnable(se); update_cfs_group(se); cfs_rq->h_nr_running++; cfs_rq->idle_h_nr_running += idle_h_nr_running; if (cfs_rq_is_idle(cfs_rq)) idle_h_nr_running = 1; /* end evaluation on encountering a throttled cfs_rq */ if (cfs_rq_throttled(cfs_rq)) goto enqueue_throttle; } /* At this point se is NULL and we are at root level*/ add_nr_running(rq, 1); /* * Since new tasks are assigned an initial util_avg equal to * half of the spare capacity of their CPU, tiny tasks have the * ability to cross the overutilized threshold, which will * result in the load balancer ruining all the task placement * done by EAS. As a way to mitigate that effect, do not account * for the first enqueue operation of new tasks during the * overutilized flag detection. * * A better way of solving this problem would be to wait for * the PELT signals of tasks to converge before taking them * into account, but that is not straightforward to implement, * and the following generally works well enough in practice. */ if (!task_new) update_overutilized_status(rq); enqueue_throttle: assert_list_leaf_cfs_rq(rq); hrtick_update(rq); } static void set_next_buddy(struct sched_entity *se); /* * The dequeue_task method is called before nr_running is * decreased. We remove the task from the rbtree and * update the fair scheduling stats: */ static void dequeue_task_fair(struct rq *rq, struct task_struct *p, int flags) { struct cfs_rq *cfs_rq; struct sched_entity *se = &p->se; int task_sleep = flags & DEQUEUE_SLEEP; int idle_h_nr_running = task_has_idle_policy(p); bool was_sched_idle = sched_idle_rq(rq); util_est_dequeue(&rq->cfs, p); for_each_sched_entity(se) { cfs_rq = cfs_rq_of(se); dequeue_entity(cfs_rq, se, flags); cfs_rq->h_nr_running--; cfs_rq->idle_h_nr_running -= idle_h_nr_running; if (cfs_rq_is_idle(cfs_rq)) idle_h_nr_running = 1; /* end evaluation on encountering a throttled cfs_rq */ if (cfs_rq_throttled(cfs_rq)) goto dequeue_throttle; /* Don't dequeue parent if it has other entities besides us */ if (cfs_rq->load.weight) { /* Avoid re-evaluating load for this entity: */ se = parent_entity(se); /* * Bias pick_next to pick a task from this cfs_rq, as * p is sleeping when it is within its sched_slice. */ if (task_sleep && se && !throttled_hierarchy(cfs_rq)) set_next_buddy(se); break; } flags |= DEQUEUE_SLEEP; } for_each_sched_entity(se) { cfs_rq = cfs_rq_of(se); update_load_avg(cfs_rq, se, UPDATE_TG); se_update_runnable(se); update_cfs_group(se); cfs_rq->h_nr_running--; cfs_rq->idle_h_nr_running -= idle_h_nr_running; if (cfs_rq_is_idle(cfs_rq)) idle_h_nr_running = 1; /* end evaluation on encountering a throttled cfs_rq */ if (cfs_rq_throttled(cfs_rq)) goto dequeue_throttle; } /* At this point se is NULL and we are at root level*/ sub_nr_running(rq, 1); /* balance early to pull high priority tasks */ if (unlikely(!was_sched_idle && sched_idle_rq(rq))) rq->next_balance = jiffies; dequeue_throttle: util_est_update(&rq->cfs, p, task_sleep); hrtick_update(rq); } #ifdef CONFIG_SMP /* Working cpumask for: load_balance, load_balance_newidle. */ static DEFINE_PER_CPU(cpumask_var_t, load_balance_mask); static DEFINE_PER_CPU(cpumask_var_t, select_rq_mask); static DEFINE_PER_CPU(cpumask_var_t, should_we_balance_tmpmask); #ifdef CONFIG_NO_HZ_COMMON static struct { cpumask_var_t idle_cpus_mask; atomic_t nr_cpus; int has_blocked; /* Idle CPUS has blocked load */ int needs_update; /* Newly idle CPUs need their next_balance collated */ unsigned long next_balance; /* in jiffy units */ unsigned long next_blocked; /* Next update of blocked load in jiffies */ } nohz ____cacheline_aligned; #endif /* CONFIG_NO_HZ_COMMON */ static unsigned long cpu_load(struct rq *rq) { return cfs_rq_load_avg(&rq->cfs); } /* * cpu_load_without - compute CPU load without any contributions from *p * @cpu: the CPU which load is requested * @p: the task which load should be discounted * * The load of a CPU is defined by the load of tasks currently enqueued on that * CPU as well as tasks which are currently sleeping after an execution on that * CPU. * * This method returns the load of the specified CPU by discounting the load of * the specified task, whenever the task is currently contributing to the CPU * load. */ static unsigned long cpu_load_without(struct rq *rq, struct task_struct *p) { struct cfs_rq *cfs_rq; unsigned int load; /* Task has no contribution or is new */ if (cpu_of(rq) != task_cpu(p) || !READ_ONCE(p->se.avg.last_update_time)) return cpu_load(rq); cfs_rq = &rq->cfs; load = READ_ONCE(cfs_rq->avg.load_avg); /* Discount task's util from CPU's util */ lsub_positive(&load, task_h_load(p)); return load; } static unsigned long cpu_runnable(struct rq *rq) { return cfs_rq_runnable_avg(&rq->cfs); } static unsigned long cpu_runnable_without(struct rq *rq, struct task_struct *p) { struct cfs_rq *cfs_rq; unsigned int runnable; /* Task has no contribution or is new */ if (cpu_of(rq) != task_cpu(p) || !READ_ONCE(p->se.avg.last_update_time)) return cpu_runnable(rq); cfs_rq = &rq->cfs; runnable = READ_ONCE(cfs_rq->avg.runnable_avg); /* Discount task's runnable from CPU's runnable */ lsub_positive(&runnable, p->se.avg.runnable_avg); return runnable; } static unsigned long capacity_of(int cpu) { return cpu_rq(cpu)->cpu_capacity; } static void record_wakee(struct task_struct *p) { /* * Only decay a single time; tasks that have less then 1 wakeup per * jiffy will not have built up many flips. */ if (time_after(jiffies, current->wakee_flip_decay_ts + HZ)) { current->wakee_flips >>= 1; current->wakee_flip_decay_ts = jiffies; } if (current->last_wakee != p) { current->last_wakee = p; current->wakee_flips++; } } /* * Detect M:N waker/wakee relationships via a switching-frequency heuristic. * * A waker of many should wake a different task than the one last awakened * at a frequency roughly N times higher than one of its wakees. * * In order to determine whether we should let the load spread vs consolidating * to shared cache, we look for a minimum 'flip' frequency of llc_size in one * partner, and a factor of lls_size higher frequency in the other. * * With both conditions met, we can be relatively sure that the relationship is * non-monogamous, with partner count exceeding socket size. * * Waker/wakee being client/server, worker/dispatcher, interrupt source or * whatever is irrelevant, spread criteria is apparent partner count exceeds * socket size. */ static int wake_wide(struct task_struct *p) { unsigned int master = current->wakee_flips; unsigned int slave = p->wakee_flips; int factor = __this_cpu_read(sd_llc_size); if (master < slave) swap(master, slave); if (slave < factor || master < slave * factor) return 0; return 1; } /* * The purpose of wake_affine() is to quickly determine on which CPU we can run * soonest. For the purpose of speed we only consider the waking and previous * CPU. * * wake_affine_idle() - only considers 'now', it check if the waking CPU is * cache-affine and is (or will be) idle. * * wake_affine_weight() - considers the weight to reflect the average * scheduling latency of the CPUs. This seems to work * for the overloaded case. */ static int wake_affine_idle(int this_cpu, int prev_cpu, int sync) { /* * If this_cpu is idle, it implies the wakeup is from interrupt * context. Only allow the move if cache is shared. Otherwise an * interrupt intensive workload could force all tasks onto one * node depending on the IO topology or IRQ affinity settings. * * If the prev_cpu is idle and cache affine then avoid a migration. * There is no guarantee that the cache hot data from an interrupt * is more important than cache hot data on the prev_cpu and from * a cpufreq perspective, it's better to have higher utilisation * on one CPU. */ if (available_idle_cpu(this_cpu) && cpus_share_cache(this_cpu, prev_cpu)) return available_idle_cpu(prev_cpu) ? prev_cpu : this_cpu; if (sync && cpu_rq(this_cpu)->nr_running == 1) return this_cpu; if (available_idle_cpu(prev_cpu)) return prev_cpu; return nr_cpumask_bits; } static int wake_affine_weight(struct sched_domain *sd, struct task_struct *p, int this_cpu, int prev_cpu, int sync) { s64 this_eff_load, prev_eff_load; unsigned long task_load; this_eff_load = cpu_load(cpu_rq(this_cpu)); if (sync) { unsigned long current_load = task_h_load(current); if (current_load > this_eff_load) return this_cpu; this_eff_load -= current_load; } task_load = task_h_load(p); this_eff_load += task_load; if (sched_feat(WA_BIAS)) this_eff_load *= 100; this_eff_load *= capacity_of(prev_cpu); prev_eff_load = cpu_load(cpu_rq(prev_cpu)); prev_eff_load -= task_load; if (sched_feat(WA_BIAS)) prev_eff_load *= 100 + (sd->imbalance_pct - 100) / 2; prev_eff_load *= capacity_of(this_cpu); /* * If sync, adjust the weight of prev_eff_load such that if * prev_eff == this_eff that select_idle_sibling() will consider * stacking the wakee on top of the waker if no other CPU is * idle. */ if (sync) prev_eff_load += 1; return this_eff_load < prev_eff_load ? this_cpu : nr_cpumask_bits; } static int wake_affine(struct sched_domain *sd, struct task_struct *p, int this_cpu, int prev_cpu, int sync) { int target = nr_cpumask_bits; if (sched_feat(WA_IDLE)) target = wake_affine_idle(this_cpu, prev_cpu, sync); if (sched_feat(WA_WEIGHT) && target == nr_cpumask_bits) target = wake_affine_weight(sd, p, this_cpu, prev_cpu, sync); schedstat_inc(p->stats.nr_wakeups_affine_attempts); if (target != this_cpu) return prev_cpu; schedstat_inc(sd->ttwu_move_affine); schedstat_inc(p->stats.nr_wakeups_affine); return target; } static struct sched_group * find_idlest_group(struct sched_domain *sd, struct task_struct *p, int this_cpu); /* * find_idlest_group_cpu - find the idlest CPU among the CPUs in the group. */ static int find_idlest_group_cpu(struct sched_group *group, struct task_struct *p, int this_cpu) { unsigned long load, min_load = ULONG_MAX; unsigned int min_exit_latency = UINT_MAX; u64 latest_idle_timestamp = 0; int least_loaded_cpu = this_cpu; int shallowest_idle_cpu = -1; int i; /* Check if we have any choice: */ if (group->group_weight == 1) return cpumask_first(sched_group_span(group)); /* Traverse only the allowed CPUs */ for_each_cpu_and(i, sched_group_span(group), p->cpus_ptr) { struct rq *rq = cpu_rq(i); if (!sched_core_cookie_match(rq, p)) continue; if (sched_idle_cpu(i)) return i; if (available_idle_cpu(i)) { struct cpuidle_state *idle = idle_get_state(rq); if (idle && idle->exit_latency < min_exit_latency) { /* * We give priority to a CPU whose idle state * has the smallest exit latency irrespective * of any idle timestamp. */ min_exit_latency = idle->exit_latency; latest_idle_timestamp = rq->idle_stamp; shallowest_idle_cpu = i; } else if ((!idle || idle->exit_latency == min_exit_latency) && rq->idle_stamp > latest_idle_timestamp) { /* * If equal or no active idle state, then * the most recently idled CPU might have * a warmer cache. */ latest_idle_timestamp = rq->idle_stamp; shallowest_idle_cpu = i; } } else if (shallowest_idle_cpu == -1) { load = cpu_load(cpu_rq(i)); if (load < min_load) { min_load = load; least_loaded_cpu = i; } } } return shallowest_idle_cpu != -1 ? shallowest_idle_cpu : least_loaded_cpu; } static inline int find_idlest_cpu(struct sched_domain *sd, struct task_struct *p, int cpu, int prev_cpu, int sd_flag) { int new_cpu = cpu; if (!cpumask_intersects(sched_domain_span(sd), p->cpus_ptr)) return prev_cpu; /* * We need task's util for cpu_util_without, sync it up to * prev_cpu's last_update_time. */ if (!(sd_flag & SD_BALANCE_FORK)) sync_entity_load_avg(&p->se); while (sd) { struct sched_group *group; struct sched_domain *tmp; int weight; if (!(sd->flags & sd_flag)) { sd = sd->child; continue; } group = find_idlest_group(sd, p, cpu); if (!group) { sd = sd->child; continue; } new_cpu = find_idlest_group_cpu(group, p, cpu); if (new_cpu == cpu) { /* Now try balancing at a lower domain level of 'cpu': */ sd = sd->child; continue; } /* Now try balancing at a lower domain level of 'new_cpu': */ cpu = new_cpu; weight = sd->span_weight; sd = NULL; for_each_domain(cpu, tmp) { if (weight <= tmp->span_weight) break; if (tmp->flags & sd_flag) sd = tmp; } } return new_cpu; } static inline int __select_idle_cpu(int cpu, struct task_struct *p) { if ((available_idle_cpu(cpu) || sched_idle_cpu(cpu)) && sched_cpu_cookie_match(cpu_rq(cpu), p)) return cpu; return -1; } #ifdef CONFIG_SCHED_SMT DEFINE_STATIC_KEY_FALSE(sched_smt_present); EXPORT_SYMBOL_GPL(sched_smt_present); static inline void set_idle_cores(int cpu, int val) { struct sched_domain_shared *sds; sds = rcu_dereference(per_cpu(sd_llc_shared, cpu)); if (sds) WRITE_ONCE(sds->has_idle_cores, val); } static inline bool test_idle_cores(int cpu) { struct sched_domain_shared *sds; sds = rcu_dereference(per_cpu(sd_llc_shared, cpu)); if (sds) return READ_ONCE(sds->has_idle_cores); return false; } /* * Scans the local SMT mask to see if the entire core is idle, and records this * information in sd_llc_shared->has_idle_cores. * * Since SMT siblings share all cache levels, inspecting this limited remote * state should be fairly cheap. */ void __update_idle_core(struct rq *rq) { int core = cpu_of(rq); int cpu; rcu_read_lock(); if (test_idle_cores(core)) goto unlock; for_each_cpu(cpu, cpu_smt_mask(core)) { if (cpu == core) continue; if (!available_idle_cpu(cpu)) goto unlock; } set_idle_cores(core, 1); unlock: rcu_read_unlock(); } /* * Scan the entire LLC domain for idle cores; this dynamically switches off if * there are no idle cores left in the system; tracked through * sd_llc->shared->has_idle_cores and enabled through update_idle_core() above. */ static int select_idle_core(struct task_struct *p, int core, struct cpumask *cpus, int *idle_cpu) { bool idle = true; int cpu; for_each_cpu(cpu, cpu_smt_mask(core)) { if (!available_idle_cpu(cpu)) { idle = false; if (*idle_cpu == -1) { if (sched_idle_cpu(cpu) && cpumask_test_cpu(cpu, p->cpus_ptr)) { *idle_cpu = cpu; break; } continue; } break; } if (*idle_cpu == -1 && cpumask_test_cpu(cpu, p->cpus_ptr)) *idle_cpu = cpu; } if (idle) return core; cpumask_andnot(cpus, cpus, cpu_smt_mask(core)); return -1; } /* * Scan the local SMT mask for idle CPUs. */ static int select_idle_smt(struct task_struct *p, int target) { int cpu; for_each_cpu_and(cpu, cpu_smt_mask(target), p->cpus_ptr) { if (cpu == target) continue; if (available_idle_cpu(cpu) || sched_idle_cpu(cpu)) return cpu; } return -1; } #else /* CONFIG_SCHED_SMT */ static inline void set_idle_cores(int cpu, int val) { } static inline bool test_idle_cores(int cpu) { return false; } static inline int select_idle_core(struct task_struct *p, int core, struct cpumask *cpus, int *idle_cpu) { return __select_idle_cpu(core, p); } static inline int select_idle_smt(struct task_struct *p, int target) { return -1; } #endif /* CONFIG_SCHED_SMT */ /* * Scan the LLC domain for idle CPUs; this is dynamically regulated by * comparing the average scan cost (tracked in sd->avg_scan_cost) against the * average idle time for this rq (as found in rq->avg_idle). */ static int select_idle_cpu(struct task_struct *p, struct sched_domain *sd, bool has_idle_core, int target) { struct cpumask *cpus = this_cpu_cpumask_var_ptr(select_rq_mask); int i, cpu, idle_cpu = -1, nr = INT_MAX; struct sched_domain_shared *sd_share; cpumask_and(cpus, sched_domain_span(sd), p->cpus_ptr); if (sched_feat(SIS_UTIL)) { sd_share = rcu_dereference(per_cpu(sd_llc_shared, target)); if (sd_share) { /* because !--nr is the condition to stop scan */ nr = READ_ONCE(sd_share->nr_idle_scan) + 1; /* overloaded LLC is unlikely to have idle cpu/core */ if (nr == 1) return -1; } } if (static_branch_unlikely(&sched_cluster_active)) { struct sched_group *sg = sd->groups; if (sg->flags & SD_CLUSTER) { for_each_cpu_wrap(cpu, sched_group_span(sg), target + 1) { if (!cpumask_test_cpu(cpu, cpus)) continue; if (has_idle_core) { i = select_idle_core(p, cpu, cpus, &idle_cpu); if ((unsigned int)i < nr_cpumask_bits) return i; } else { if (--nr <= 0) return -1; idle_cpu = __select_idle_cpu(cpu, p); if ((unsigned int)idle_cpu < nr_cpumask_bits) return idle_cpu; } } cpumask_andnot(cpus, cpus, sched_group_span(sg)); } } for_each_cpu_wrap(cpu, cpus, target + 1) { if (has_idle_core) { i = select_idle_core(p, cpu, cpus, &idle_cpu); if ((unsigned int)i < nr_cpumask_bits) return i; } else { if (--nr <= 0) return -1; idle_cpu = __select_idle_cpu(cpu, p); if ((unsigned int)idle_cpu < nr_cpumask_bits) break; } } if (has_idle_core) set_idle_cores(target, false); return idle_cpu; } /* * Scan the asym_capacity domain for idle CPUs; pick the first idle one on which * the task fits. If no CPU is big enough, but there are idle ones, try to * maximize capacity. */ static int select_idle_capacity(struct task_struct *p, struct sched_domain *sd, int target) { unsigned long task_util, util_min, util_max, best_cap = 0; int fits, best_fits = 0; int cpu, best_cpu = -1; struct cpumask *cpus; cpus = this_cpu_cpumask_var_ptr(select_rq_mask); cpumask_and(cpus, sched_domain_span(sd), p->cpus_ptr); task_util = task_util_est(p); util_min = uclamp_eff_value(p, UCLAMP_MIN); util_max = uclamp_eff_value(p, UCLAMP_MAX); for_each_cpu_wrap(cpu, cpus, target) { unsigned long cpu_cap = capacity_of(cpu); if (!available_idle_cpu(cpu) && !sched_idle_cpu(cpu)) continue; fits = util_fits_cpu(task_util, util_min, util_max, cpu); /* This CPU fits with all requirements */ if (fits > 0) return cpu; /* * Only the min performance hint (i.e. uclamp_min) doesn't fit. * Look for the CPU with best capacity. */ else if (fits < 0) cpu_cap = arch_scale_cpu_capacity(cpu) - thermal_load_avg(cpu_rq(cpu)); /* * First, select CPU which fits better (-1 being better than 0). * Then, select the one with best capacity at same level. */ if ((fits < best_fits) || ((fits == best_fits) && (cpu_cap > best_cap))) { best_cap = cpu_cap; best_cpu = cpu; best_fits = fits; } } return best_cpu; } static inline bool asym_fits_cpu(unsigned long util, unsigned long util_min, unsigned long util_max, int cpu) { if (sched_asym_cpucap_active()) /* * Return true only if the cpu fully fits the task requirements * which include the utilization and the performance hints. */ return (util_fits_cpu(util, util_min, util_max, cpu) > 0); return true; } /* * Try and locate an idle core/thread in the LLC cache domain. */ static int select_idle_sibling(struct task_struct *p, int prev, int target) { bool has_idle_core = false; struct sched_domain *sd; unsigned long task_util, util_min, util_max; int i, recent_used_cpu, prev_aff = -1; /* * On asymmetric system, update task utilization because we will check * that the task fits with cpu's capacity. */ if (sched_asym_cpucap_active()) { sync_entity_load_avg(&p->se); task_util = task_util_est(p); util_min = uclamp_eff_value(p, UCLAMP_MIN); util_max = uclamp_eff_value(p, UCLAMP_MAX); } /* * per-cpu select_rq_mask usage */ lockdep_assert_irqs_disabled(); if ((available_idle_cpu(target) || sched_idle_cpu(target)) && asym_fits_cpu(task_util, util_min, util_max, target)) return target; /* * If the previous CPU is cache affine and idle, don't be stupid: */ if (prev != target && cpus_share_cache(prev, target) && (available_idle_cpu(prev) || sched_idle_cpu(prev)) && asym_fits_cpu(task_util, util_min, util_max, prev)) { if (!static_branch_unlikely(&sched_cluster_active) || cpus_share_resources(prev, target)) return prev; prev_aff = prev; } /* * Allow a per-cpu kthread to stack with the wakee if the * kworker thread and the tasks previous CPUs are the same. * The assumption is that the wakee queued work for the * per-cpu kthread that is now complete and the wakeup is * essentially a sync wakeup. An obvious example of this * pattern is IO completions. */ if (is_per_cpu_kthread(current) && in_task() && prev == smp_processor_id() && this_rq()->nr_running <= 1 && asym_fits_cpu(task_util, util_min, util_max, prev)) { return prev; } /* Check a recently used CPU as a potential idle candidate: */ recent_used_cpu = p->recent_used_cpu; p->recent_used_cpu = prev; if (recent_used_cpu != prev && recent_used_cpu != target && cpus_share_cache(recent_used_cpu, target) && (available_idle_cpu(recent_used_cpu) || sched_idle_cpu(recent_used_cpu)) && cpumask_test_cpu(recent_used_cpu, p->cpus_ptr) && asym_fits_cpu(task_util, util_min, util_max, recent_used_cpu)) { if (!static_branch_unlikely(&sched_cluster_active) || cpus_share_resources(recent_used_cpu, target)) return recent_used_cpu; } else { recent_used_cpu = -1; } /* * For asymmetric CPU capacity systems, our domain of interest is * sd_asym_cpucapacity rather than sd_llc. */ if (sched_asym_cpucap_active()) { sd = rcu_dereference(per_cpu(sd_asym_cpucapacity, target)); /* * On an asymmetric CPU capacity system where an exclusive * cpuset defines a symmetric island (i.e. one unique * capacity_orig value through the cpuset), the key will be set * but the CPUs within that cpuset will not have a domain with * SD_ASYM_CPUCAPACITY. These should follow the usual symmetric * capacity path. */ if (sd) { i = select_idle_capacity(p, sd, target); return ((unsigned)i < nr_cpumask_bits) ? i : target; } } sd = rcu_dereference(per_cpu(sd_llc, target)); if (!sd) return target; if (sched_smt_active()) { has_idle_core = test_idle_cores(target); if (!has_idle_core && cpus_share_cache(prev, target)) { i = select_idle_smt(p, prev); if ((unsigned int)i < nr_cpumask_bits) return i; } } i = select_idle_cpu(p, sd, has_idle_core, target); if ((unsigned)i < nr_cpumask_bits) return i; /* * For cluster machines which have lower sharing cache like L2 or * LLC Tag, we tend to find an idle CPU in the target's cluster * first. But prev_cpu or recent_used_cpu may also be a good candidate, * use them if possible when no idle CPU found in select_idle_cpu(). */ if ((unsigned int)prev_aff < nr_cpumask_bits) return prev_aff; if ((unsigned int)recent_used_cpu < nr_cpumask_bits) return recent_used_cpu; return target; } /** * cpu_util() - Estimates the amount of CPU capacity used by CFS tasks. * @cpu: the CPU to get the utilization for * @p: task for which the CPU utilization should be predicted or NULL * @dst_cpu: CPU @p migrates to, -1 if @p moves from @cpu or @p == NULL * @boost: 1 to enable boosting, otherwise 0 * * The unit of the return value must be the same as the one of CPU capacity * so that CPU utilization can be compared with CPU capacity. * * CPU utilization is the sum of running time of runnable tasks plus the * recent utilization of currently non-runnable tasks on that CPU. * It represents the amount of CPU capacity currently used by CFS tasks in * the range [0..max CPU capacity] with max CPU capacity being the CPU * capacity at f_max. * * The estimated CPU utilization is defined as the maximum between CPU * utilization and sum of the estimated utilization of the currently * runnable tasks on that CPU. It preserves a utilization "snapshot" of * previously-executed tasks, which helps better deduce how busy a CPU will * be when a long-sleeping task wakes up. The contribution to CPU utilization * of such a task would be significantly decayed at this point of time. * * Boosted CPU utilization is defined as max(CPU runnable, CPU utilization). * CPU contention for CFS tasks can be detected by CPU runnable > CPU * utilization. Boosting is implemented in cpu_util() so that internal * users (e.g. EAS) can use it next to external users (e.g. schedutil), * latter via cpu_util_cfs_boost(). * * CPU utilization can be higher than the current CPU capacity * (f_curr/f_max * max CPU capacity) or even the max CPU capacity because * of rounding errors as well as task migrations or wakeups of new tasks. * CPU utilization has to be capped to fit into the [0..max CPU capacity] * range. Otherwise a group of CPUs (CPU0 util = 121% + CPU1 util = 80%) * could be seen as over-utilized even though CPU1 has 20% of spare CPU * capacity. CPU utilization is allowed to overshoot current CPU capacity * though since this is useful for predicting the CPU capacity required * after task migrations (scheduler-driven DVFS). * * Return: (Boosted) (estimated) utilization for the specified CPU. */ static unsigned long cpu_util(int cpu, struct task_struct *p, int dst_cpu, int boost) { struct cfs_rq *cfs_rq = &cpu_rq(cpu)->cfs; unsigned long util = READ_ONCE(cfs_rq->avg.util_avg); unsigned long runnable; if (boost) { runnable = READ_ONCE(cfs_rq->avg.runnable_avg); util = max(util, runnable); } /* * If @dst_cpu is -1 or @p migrates from @cpu to @dst_cpu remove its * contribution. If @p migrates from another CPU to @cpu add its * contribution. In all the other cases @cpu is not impacted by the * migration so its util_avg is already correct. */ if (p && task_cpu(p) == cpu && dst_cpu != cpu) lsub_positive(&util, task_util(p)); else if (p && task_cpu(p) != cpu && dst_cpu == cpu) util += task_util(p); if (sched_feat(UTIL_EST)) { unsigned long util_est; util_est = READ_ONCE(cfs_rq->avg.util_est.enqueued); /* * During wake-up @p isn't enqueued yet and doesn't contribute * to any cpu_rq(cpu)->cfs.avg.util_est.enqueued. * If @dst_cpu == @cpu add it to "simulate" cpu_util after @p * has been enqueued. * * During exec (@dst_cpu = -1) @p is enqueued and does * contribute to cpu_rq(cpu)->cfs.util_est.enqueued. * Remove it to "simulate" cpu_util without @p's contribution. * * Despite the task_on_rq_queued(@p) check there is still a * small window for a possible race when an exec * select_task_rq_fair() races with LB's detach_task(). * * detach_task() * deactivate_task() * p->on_rq = TASK_ON_RQ_MIGRATING; * -------------------------------- A * dequeue_task() \ * dequeue_task_fair() + Race Time * util_est_dequeue() / * -------------------------------- B * * The additional check "current == p" is required to further * reduce the race window. */ if (dst_cpu == cpu) util_est += _task_util_est(p); else if (p && unlikely(task_on_rq_queued(p) || current == p)) lsub_positive(&util_est, _task_util_est(p)); util = max(util, util_est); } return min(util, arch_scale_cpu_capacity(cpu)); } unsigned long cpu_util_cfs(int cpu) { return cpu_util(cpu, NULL, -1, 0); } unsigned long cpu_util_cfs_boost(int cpu) { return cpu_util(cpu, NULL, -1, 1); } /* * cpu_util_without: compute cpu utilization without any contributions from *p * @cpu: the CPU which utilization is requested * @p: the task which utilization should be discounted * * The utilization of a CPU is defined by the utilization of tasks currently * enqueued on that CPU as well as tasks which are currently sleeping after an * execution on that CPU. * * This method returns the utilization of the specified CPU by discounting the * utilization of the specified task, whenever the task is currently * contributing to the CPU utilization. */ static unsigned long cpu_util_without(int cpu, struct task_struct *p) { /* Task has no contribution or is new */ if (cpu != task_cpu(p) || !READ_ONCE(p->se.avg.last_update_time)) p = NULL; return cpu_util(cpu, p, -1, 0); } /* * energy_env - Utilization landscape for energy estimation. * @task_busy_time: Utilization contribution by the task for which we test the * placement. Given by eenv_task_busy_time(). * @pd_busy_time: Utilization of the whole perf domain without the task * contribution. Given by eenv_pd_busy_time(). * @cpu_cap: Maximum CPU capacity for the perf domain. * @pd_cap: Entire perf domain capacity. (pd->nr_cpus * cpu_cap). */ struct energy_env { unsigned long task_busy_time; unsigned long pd_busy_time; unsigned long cpu_cap; unsigned long pd_cap; }; /* * Compute the task busy time for compute_energy(). This time cannot be * injected directly into effective_cpu_util() because of the IRQ scaling. * The latter only makes sense with the most recent CPUs where the task has * run. */ static inline void eenv_task_busy_time(struct energy_env *eenv, struct task_struct *p, int prev_cpu) { unsigned long busy_time, max_cap = arch_scale_cpu_capacity(prev_cpu); unsigned long irq = cpu_util_irq(cpu_rq(prev_cpu)); if (unlikely(irq >= max_cap)) busy_time = max_cap; else busy_time = scale_irq_capacity(task_util_est(p), irq, max_cap); eenv->task_busy_time = busy_time; } /* * Compute the perf_domain (PD) busy time for compute_energy(). Based on the * utilization for each @pd_cpus, it however doesn't take into account * clamping since the ratio (utilization / cpu_capacity) is already enough to * scale the EM reported power consumption at the (eventually clamped) * cpu_capacity. * * The contribution of the task @p for which we want to estimate the * energy cost is removed (by cpu_util()) and must be calculated * separately (see eenv_task_busy_time). This ensures: * * - A stable PD utilization, no matter which CPU of that PD we want to place * the task on. * * - A fair comparison between CPUs as the task contribution (task_util()) * will always be the same no matter which CPU utilization we rely on * (util_avg or util_est). * * Set @eenv busy time for the PD that spans @pd_cpus. This busy time can't * exceed @eenv->pd_cap. */ static inline void eenv_pd_busy_time(struct energy_env *eenv, struct cpumask *pd_cpus, struct task_struct *p) { unsigned long busy_time = 0; int cpu; for_each_cpu(cpu, pd_cpus) { unsigned long util = cpu_util(cpu, p, -1, 0); busy_time += effective_cpu_util(cpu, util, ENERGY_UTIL, NULL); } eenv->pd_busy_time = min(eenv->pd_cap, busy_time); } /* * Compute the maximum utilization for compute_energy() when the task @p * is placed on the cpu @dst_cpu. * * Returns the maximum utilization among @eenv->cpus. This utilization can't * exceed @eenv->cpu_cap. */ static inline unsigned long eenv_pd_max_util(struct energy_env *eenv, struct cpumask *pd_cpus, struct task_struct *p, int dst_cpu) { unsigned long max_util = 0; int cpu; for_each_cpu(cpu, pd_cpus) { struct task_struct *tsk = (cpu == dst_cpu) ? p : NULL; unsigned long util = cpu_util(cpu, p, dst_cpu, 1); unsigned long eff_util; /* * Performance domain frequency: utilization clamping * must be considered since it affects the selection * of the performance domain frequency. * NOTE: in case RT tasks are running, by default the * FREQUENCY_UTIL's utilization can be max OPP. */ eff_util = effective_cpu_util(cpu, util, FREQUENCY_UTIL, tsk); max_util = max(max_util, eff_util); } return min(max_util, eenv->cpu_cap); } /* * compute_energy(): Use the Energy Model to estimate the energy that @pd would * consume for a given utilization landscape @eenv. When @dst_cpu < 0, the task * contribution is ignored. */ static inline unsigned long compute_energy(struct energy_env *eenv, struct perf_domain *pd, struct cpumask *pd_cpus, struct task_struct *p, int dst_cpu) { unsigned long max_util = eenv_pd_max_util(eenv, pd_cpus, p, dst_cpu); unsigned long busy_time = eenv->pd_busy_time; unsigned long energy; if (dst_cpu >= 0) busy_time = min(eenv->pd_cap, busy_time + eenv->task_busy_time); energy = em_cpu_energy(pd->em_pd, max_util, busy_time, eenv->cpu_cap); trace_sched_compute_energy_tp(p, dst_cpu, energy, max_util, busy_time); return energy; } /* * find_energy_efficient_cpu(): Find most energy-efficient target CPU for the * waking task. find_energy_efficient_cpu() looks for the CPU with maximum * spare capacity in each performance domain and uses it as a potential * candidate to execute the task. Then, it uses the Energy Model to figure * out which of the CPU candidates is the most energy-efficient. * * The rationale for this heuristic is as follows. In a performance domain, * all the most energy efficient CPU candidates (according to the Energy * Model) are those for which we'll request a low frequency. When there are * several CPUs for which the frequency request will be the same, we don't * have enough data to break the tie between them, because the Energy Model * only includes active power costs. With this model, if we assume that * frequency requests follow utilization (e.g. using schedutil), the CPU with * the maximum spare capacity in a performance domain is guaranteed to be among * the best candidates of the performance domain. * * In practice, it could be preferable from an energy standpoint to pack * small tasks on a CPU in order to let other CPUs go in deeper idle states, * but that could also hurt our chances to go cluster idle, and we have no * ways to tell with the current Energy Model if this is actually a good * idea or not. So, find_energy_efficient_cpu() basically favors * cluster-packing, and spreading inside a cluster. That should at least be * a good thing for latency, and this is consistent with the idea that most * of the energy savings of EAS come from the asymmetry of the system, and * not so much from breaking the tie between identical CPUs. That's also the * reason why EAS is enabled in the topology code only for systems where * SD_ASYM_CPUCAPACITY is set. * * NOTE: Forkees are not accepted in the energy-aware wake-up path because * they don't have any useful utilization data yet and it's not possible to * forecast their impact on energy consumption. Consequently, they will be * placed by find_idlest_cpu() on the least loaded CPU, which might turn out * to be energy-inefficient in some use-cases. The alternative would be to * bias new tasks towards specific types of CPUs first, or to try to infer * their util_avg from the parent task, but those heuristics could hurt * other use-cases too. So, until someone finds a better way to solve this, * let's keep things simple by re-using the existing slow path. */ static int find_energy_efficient_cpu(struct task_struct *p, int prev_cpu) { struct cpumask *cpus = this_cpu_cpumask_var_ptr(select_rq_mask); unsigned long prev_delta = ULONG_MAX, best_delta = ULONG_MAX; unsigned long p_util_min = uclamp_is_used() ? uclamp_eff_value(p, UCLAMP_MIN) : 0; unsigned long p_util_max = uclamp_is_used() ? uclamp_eff_value(p, UCLAMP_MAX) : 1024; struct root_domain *rd = this_rq()->rd; int cpu, best_energy_cpu, target = -1; int prev_fits = -1, best_fits = -1; unsigned long best_thermal_cap = 0; unsigned long prev_thermal_cap = 0; struct sched_domain *sd; struct perf_domain *pd; struct energy_env eenv; rcu_read_lock(); pd = rcu_dereference(rd->pd); if (!pd || READ_ONCE(rd->overutilized)) goto unlock; /* * Energy-aware wake-up happens on the lowest sched_domain starting * from sd_asym_cpucapacity spanning over this_cpu and prev_cpu. */ sd = rcu_dereference(*this_cpu_ptr(&sd_asym_cpucapacity)); while (sd && !cpumask_test_cpu(prev_cpu, sched_domain_span(sd))) sd = sd->parent; if (!sd) goto unlock; target = prev_cpu; sync_entity_load_avg(&p->se); if (!task_util_est(p) && p_util_min == 0) goto unlock; eenv_task_busy_time(&eenv, p, prev_cpu); for (; pd; pd = pd->next) { unsigned long util_min = p_util_min, util_max = p_util_max; unsigned long cpu_cap, cpu_thermal_cap, util; long prev_spare_cap = -1, max_spare_cap = -1; unsigned long rq_util_min, rq_util_max; unsigned long cur_delta, base_energy; int max_spare_cap_cpu = -1; int fits, max_fits = -1; cpumask_and(cpus, perf_domain_span(pd), cpu_online_mask); if (cpumask_empty(cpus)) continue; /* Account thermal pressure for the energy estimation */ cpu = cpumask_first(cpus); cpu_thermal_cap = arch_scale_cpu_capacity(cpu); cpu_thermal_cap -= arch_scale_thermal_pressure(cpu); eenv.cpu_cap = cpu_thermal_cap; eenv.pd_cap = 0; for_each_cpu(cpu, cpus) { struct rq *rq = cpu_rq(cpu); eenv.pd_cap += cpu_thermal_cap; if (!cpumask_test_cpu(cpu, sched_domain_span(sd))) continue; if (!cpumask_test_cpu(cpu, p->cpus_ptr)) continue; util = cpu_util(cpu, p, cpu, 0); cpu_cap = capacity_of(cpu); /* * Skip CPUs that cannot satisfy the capacity request. * IOW, placing the task there would make the CPU * overutilized. Take uclamp into account to see how * much capacity we can get out of the CPU; this is * aligned with sched_cpu_util(). */ if (uclamp_is_used() && !uclamp_rq_is_idle(rq)) { /* * Open code uclamp_rq_util_with() except for * the clamp() part. Ie: apply max aggregation * only. util_fits_cpu() logic requires to * operate on non clamped util but must use the * max-aggregated uclamp_{min, max}. */ rq_util_min = uclamp_rq_get(rq, UCLAMP_MIN); rq_util_max = uclamp_rq_get(rq, UCLAMP_MAX); util_min = max(rq_util_min, p_util_min); util_max = max(rq_util_max, p_util_max); } fits = util_fits_cpu(util, util_min, util_max, cpu); if (!fits) continue; lsub_positive(&cpu_cap, util); if (cpu == prev_cpu) { /* Always use prev_cpu as a candidate. */ prev_spare_cap = cpu_cap; prev_fits = fits; } else if ((fits > max_fits) || ((fits == max_fits) && ((long)cpu_cap > max_spare_cap))) { /* * Find the CPU with the maximum spare capacity * among the remaining CPUs in the performance * domain. */ max_spare_cap = cpu_cap; max_spare_cap_cpu = cpu; max_fits = fits; } } if (max_spare_cap_cpu < 0 && prev_spare_cap < 0) continue; eenv_pd_busy_time(&eenv, cpus, p); /* Compute the 'base' energy of the pd, without @p */ base_energy = compute_energy(&eenv, pd, cpus, p, -1); /* Evaluate the energy impact of using prev_cpu. */ if (prev_spare_cap > -1) { prev_delta = compute_energy(&eenv, pd, cpus, p, prev_cpu); /* CPU utilization has changed */ if (prev_delta < base_energy) goto unlock; prev_delta -= base_energy; prev_thermal_cap = cpu_thermal_cap; best_delta = min(best_delta, prev_delta); } /* Evaluate the energy impact of using max_spare_cap_cpu. */ if (max_spare_cap_cpu >= 0 && max_spare_cap > prev_spare_cap) { /* Current best energy cpu fits better */ if (max_fits < best_fits) continue; /* * Both don't fit performance hint (i.e. uclamp_min) * but best energy cpu has better capacity. */ if ((max_fits < 0) && (cpu_thermal_cap <= best_thermal_cap)) continue; cur_delta = compute_energy(&eenv, pd, cpus, p, max_spare_cap_cpu); /* CPU utilization has changed */ if (cur_delta < base_energy) goto unlock; cur_delta -= base_energy; /* * Both fit for the task but best energy cpu has lower * energy impact. */ if ((max_fits > 0) && (best_fits > 0) && (cur_delta >= best_delta)) continue; best_delta = cur_delta; best_energy_cpu = max_spare_cap_cpu; best_fits = max_fits; best_thermal_cap = cpu_thermal_cap; } } rcu_read_unlock(); if ((best_fits > prev_fits) || ((best_fits > 0) && (best_delta < prev_delta)) || ((best_fits < 0) && (best_thermal_cap > prev_thermal_cap))) target = best_energy_cpu; return target; unlock: rcu_read_unlock(); return target; } /* * select_task_rq_fair: Select target runqueue for the waking task in domains * that have the relevant SD flag set. In practice, this is SD_BALANCE_WAKE, * SD_BALANCE_FORK, or SD_BALANCE_EXEC. * * Balances load by selecting the idlest CPU in the idlest group, or under * certain conditions an idle sibling CPU if the domain has SD_WAKE_AFFINE set. * * Returns the target CPU number. */ static int select_task_rq_fair(struct task_struct *p, int prev_cpu, int wake_flags) { int sync = (wake_flags & WF_SYNC) && !(current->flags & PF_EXITING); struct sched_domain *tmp, *sd = NULL; int cpu = smp_processor_id(); int new_cpu = prev_cpu; int want_affine = 0; /* SD_flags and WF_flags share the first nibble */ int sd_flag = wake_flags & 0xF; /* * required for stable ->cpus_allowed */ lockdep_assert_held(&p->pi_lock); if (wake_flags & WF_TTWU) { record_wakee(p); if ((wake_flags & WF_CURRENT_CPU) && cpumask_test_cpu(cpu, p->cpus_ptr)) return cpu; if (sched_energy_enabled()) { new_cpu = find_energy_efficient_cpu(p, prev_cpu); if (new_cpu >= 0) return new_cpu; new_cpu = prev_cpu; } want_affine = !wake_wide(p) && cpumask_test_cpu(cpu, p->cpus_ptr); } rcu_read_lock(); for_each_domain(cpu, tmp) { /* * If both 'cpu' and 'prev_cpu' are part of this domain, * cpu is a valid SD_WAKE_AFFINE target. */ if (want_affine && (tmp->flags & SD_WAKE_AFFINE) && cpumask_test_cpu(prev_cpu, sched_domain_span(tmp))) { if (cpu != prev_cpu) new_cpu = wake_affine(tmp, p, cpu, prev_cpu, sync); sd = NULL; /* Prefer wake_affine over balance flags */ break; } /* * Usually only true for WF_EXEC and WF_FORK, as sched_domains * usually do not have SD_BALANCE_WAKE set. That means wakeup * will usually go to the fast path. */ if (tmp->flags & sd_flag) sd = tmp; else if (!want_affine) break; } if (unlikely(sd)) { /* Slow path */ new_cpu = find_idlest_cpu(sd, p, cpu, prev_cpu, sd_flag); } else if (wake_flags & WF_TTWU) { /* XXX always ? */ /* Fast path */ new_cpu = select_idle_sibling(p, prev_cpu, new_cpu); } rcu_read_unlock(); return new_cpu; } /* * Called immediately before a task is migrated to a new CPU; task_cpu(p) and * cfs_rq_of(p) references at time of call are still valid and identify the * previous CPU. The caller guarantees p->pi_lock or task_rq(p)->lock is held. */ static void migrate_task_rq_fair(struct task_struct *p, int new_cpu) { struct sched_entity *se = &p->se; if (!task_on_rq_migrating(p)) { remove_entity_load_avg(se); /* * Here, the task's PELT values have been updated according to * the current rq's clock. But if that clock hasn't been * updated in a while, a substantial idle time will be missed, * leading to an inflation after wake-up on the new rq. * * Estimate the missing time from the cfs_rq last_update_time * and update sched_avg to improve the PELT continuity after * migration. */ migrate_se_pelt_lag(se); } /* Tell new CPU we are migrated */ se->avg.last_update_time = 0; update_scan_period(p, new_cpu); } static void task_dead_fair(struct task_struct *p) { remove_entity_load_avg(&p->se); } static int balance_fair(struct rq *rq, struct task_struct *prev, struct rq_flags *rf) { if (rq->nr_running) return 1; return newidle_balance(rq, rf) != 0; } #endif /* CONFIG_SMP */ static void set_next_buddy(struct sched_entity *se) { for_each_sched_entity(se) { if (SCHED_WARN_ON(!se->on_rq)) return; if (se_is_idle(se)) return; cfs_rq_of(se)->next = se; } } /* * Preempt the current task with a newly woken task if needed: */ static void check_preempt_wakeup_fair(struct rq *rq, struct task_struct *p, int wake_flags) { struct task_struct *curr = rq->curr; struct sched_entity *se = &curr->se, *pse = &p->se; struct cfs_rq *cfs_rq = task_cfs_rq(curr); int next_buddy_marked = 0; int cse_is_idle, pse_is_idle; if (unlikely(se == pse)) return; /* * This is possible from callers such as attach_tasks(), in which we * unconditionally wakeup_preempt() after an enqueue (which may have * lead to a throttle). This both saves work and prevents false * next-buddy nomination below. */ if (unlikely(throttled_hierarchy(cfs_rq_of(pse)))) return; if (sched_feat(NEXT_BUDDY) && !(wake_flags & WF_FORK)) { set_next_buddy(pse); next_buddy_marked = 1; } /* * We can come here with TIF_NEED_RESCHED already set from new task * wake up path. * * Note: this also catches the edge-case of curr being in a throttled * group (e.g. via set_curr_task), since update_curr() (in the * enqueue of curr) will have resulted in resched being set. This * prevents us from potentially nominating it as a false LAST_BUDDY * below. */ if (test_tsk_need_resched(curr)) return; /* Idle tasks are by definition preempted by non-idle tasks. */ if (unlikely(task_has_idle_policy(curr)) && likely(!task_has_idle_policy(p))) goto preempt; /* * Batch and idle tasks do not preempt non-idle tasks (their preemption * is driven by the tick): */ if (unlikely(p->policy != SCHED_NORMAL) || !sched_feat(WAKEUP_PREEMPTION)) return; find_matching_se(&se, &pse); WARN_ON_ONCE(!pse); cse_is_idle = se_is_idle(se); pse_is_idle = se_is_idle(pse); /* * Preempt an idle group in favor of a non-idle group (and don't preempt * in the inverse case). */ if (cse_is_idle && !pse_is_idle) goto preempt; if (cse_is_idle != pse_is_idle) return; cfs_rq = cfs_rq_of(se); update_curr(cfs_rq); /* * XXX pick_eevdf(cfs_rq) != se ? */ if (pick_eevdf(cfs_rq) == pse) goto preempt; return; preempt: resched_curr(rq); } #ifdef CONFIG_SMP static struct task_struct *pick_task_fair(struct rq *rq) { struct sched_entity *se; struct cfs_rq *cfs_rq; again: cfs_rq = &rq->cfs; if (!cfs_rq->nr_running) return NULL; do { struct sched_entity *curr = cfs_rq->curr; /* When we pick for a remote RQ, we'll not have done put_prev_entity() */ if (curr) { if (curr->on_rq) update_curr(cfs_rq); else curr = NULL; if (unlikely(check_cfs_rq_runtime(cfs_rq))) goto again; } se = pick_next_entity(cfs_rq); cfs_rq = group_cfs_rq(se); } while (cfs_rq); return task_of(se); } #endif struct task_struct * pick_next_task_fair(struct rq *rq, struct task_struct *prev, struct rq_flags *rf) { struct cfs_rq *cfs_rq = &rq->cfs; struct sched_entity *se; struct task_struct *p; int new_tasks; again: if (!sched_fair_runnable(rq)) goto idle; #ifdef CONFIG_FAIR_GROUP_SCHED if (!prev || prev->sched_class != &fair_sched_class) goto simple; /* * Because of the set_next_buddy() in dequeue_task_fair() it is rather * likely that a next task is from the same cgroup as the current. * * Therefore attempt to avoid putting and setting the entire cgroup * hierarchy, only change the part that actually changes. */ do { struct sched_entity *curr = cfs_rq->curr; /* * Since we got here without doing put_prev_entity() we also * have to consider cfs_rq->curr. If it is still a runnable * entity, update_curr() will update its vruntime, otherwise * forget we've ever seen it. */ if (curr) { if (curr->on_rq) update_curr(cfs_rq); else curr = NULL; /* * This call to check_cfs_rq_runtime() will do the * throttle and dequeue its entity in the parent(s). * Therefore the nr_running test will indeed * be correct. */ if (unlikely(check_cfs_rq_runtime(cfs_rq))) { cfs_rq = &rq->cfs; if (!cfs_rq->nr_running) goto idle; goto simple; } } se = pick_next_entity(cfs_rq); cfs_rq = group_cfs_rq(se); } while (cfs_rq); p = task_of(se); /* * Since we haven't yet done put_prev_entity and if the selected task * is a different task than we started out with, try and touch the * least amount of cfs_rqs. */ if (prev != p) { struct sched_entity *pse = &prev->se; while (!(cfs_rq = is_same_group(se, pse))) { int se_depth = se->depth; int pse_depth = pse->depth; if (se_depth <= pse_depth) { put_prev_entity(cfs_rq_of(pse), pse); pse = parent_entity(pse); } if (se_depth >= pse_depth) { set_next_entity(cfs_rq_of(se), se); se = parent_entity(se); } } put_prev_entity(cfs_rq, pse); set_next_entity(cfs_rq, se); } goto done; simple: #endif if (prev) put_prev_task(rq, prev); do { se = pick_next_entity(cfs_rq); set_next_entity(cfs_rq, se); cfs_rq = group_cfs_rq(se); } while (cfs_rq); p = task_of(se); done: __maybe_unused; #ifdef CONFIG_SMP /* * Move the next running task to the front of * the list, so our cfs_tasks list becomes MRU * one. */ list_move(&p->se.group_node, &rq->cfs_tasks); #endif if (hrtick_enabled_fair(rq)) hrtick_start_fair(rq, p); update_misfit_status(p, rq); sched_fair_update_stop_tick(rq, p); return p; idle: if (!rf) return NULL; new_tasks = newidle_balance(rq, rf); /* * Because newidle_balance() releases (and re-acquires) rq->lock, it is * possible for any higher priority task to appear. In that case we * must re-start the pick_next_entity() loop. */ if (new_tasks < 0) return RETRY_TASK; if (new_tasks > 0) goto again; /* * rq is about to be idle, check if we need to update the * lost_idle_time of clock_pelt */ update_idle_rq_clock_pelt(rq); return NULL; } static struct task_struct *__pick_next_task_fair(struct rq *rq) { return pick_next_task_fair(rq, NULL, NULL); } /* * Account for a descheduled task: */ static void put_prev_task_fair(struct rq *rq, struct task_struct *prev) { struct sched_entity *se = &prev->se; struct cfs_rq *cfs_rq; for_each_sched_entity(se) { cfs_rq = cfs_rq_of(se); put_prev_entity(cfs_rq, se); } } /* * sched_yield() is very simple */ static void yield_task_fair(struct rq *rq) { struct task_struct *curr = rq->curr; struct cfs_rq *cfs_rq = task_cfs_rq(curr); struct sched_entity *se = &curr->se; /* * Are we the only task in the tree? */ if (unlikely(rq->nr_running == 1)) return; clear_buddies(cfs_rq, se); update_rq_clock(rq); /* * Update run-time statistics of the 'current'. */ update_curr(cfs_rq); /* * Tell update_rq_clock() that we've just updated, * so we don't do microscopic update in schedule() * and double the fastpath cost. */ rq_clock_skip_update(rq); se->deadline += calc_delta_fair(se->slice, se); } static bool yield_to_task_fair(struct rq *rq, struct task_struct *p) { struct sched_entity *se = &p->se; /* throttled hierarchies are not runnable */ if (!se->on_rq || throttled_hierarchy(cfs_rq_of(se))) return false; /* Tell the scheduler that we'd really like pse to run next. */ set_next_buddy(se); yield_task_fair(rq); return true; } #ifdef CONFIG_SMP /************************************************** * Fair scheduling class load-balancing methods. * * BASICS * * The purpose of load-balancing is to achieve the same basic fairness the * per-CPU scheduler provides, namely provide a proportional amount of compute * time to each task. This is expressed in the following equation: * * W_i,n/P_i == W_j,n/P_j for all i,j (1) * * Where W_i,n is the n-th weight average for CPU i. The instantaneous weight * W_i,0 is defined as: * * W_i,0 = \Sum_j w_i,j (2) * * Where w_i,j is the weight of the j-th runnable task on CPU i. This weight * is derived from the nice value as per sched_prio_to_weight[]. * * The weight average is an exponential decay average of the instantaneous * weight: * * W'_i,n = (2^n - 1) / 2^n * W_i,n + 1 / 2^n * W_i,0 (3) * * C_i is the compute capacity of CPU i, typically it is the * fraction of 'recent' time available for SCHED_OTHER task execution. But it * can also include other factors [XXX]. * * To achieve this balance we define a measure of imbalance which follows * directly from (1): * * imb_i,j = max{ avg(W/C), W_i/C_i } - min{ avg(W/C), W_j/C_j } (4) * * We them move tasks around to minimize the imbalance. In the continuous * function space it is obvious this converges, in the discrete case we get * a few fun cases generally called infeasible weight scenarios. * * [XXX expand on: * - infeasible weights; * - local vs global optima in the discrete case. ] * * * SCHED DOMAINS * * In order to solve the imbalance equation (4), and avoid the obvious O(n^2) * for all i,j solution, we create a tree of CPUs that follows the hardware * topology where each level pairs two lower groups (or better). This results * in O(log n) layers. Furthermore we reduce the number of CPUs going up the * tree to only the first of the previous level and we decrease the frequency * of load-balance at each level inv. proportional to the number of CPUs in * the groups. * * This yields: * * log_2 n 1 n * \Sum { --- * --- * 2^i } = O(n) (5) * i = 0 2^i 2^i * `- size of each group * | | `- number of CPUs doing load-balance * | `- freq * `- sum over all levels * * Coupled with a limit on how many tasks we can migrate every balance pass, * this makes (5) the runtime complexity of the balancer. * * An important property here is that each CPU is still (indirectly) connected * to every other CPU in at most O(log n) steps: * * The adjacency matrix of the resulting graph is given by: * * log_2 n * A_i,j = \Union (i % 2^k == 0) && i / 2^(k+1) == j / 2^(k+1) (6) * k = 0 * * And you'll find that: * * A^(log_2 n)_i,j != 0 for all i,j (7) * * Showing there's indeed a path between every CPU in at most O(log n) steps. * The task movement gives a factor of O(m), giving a convergence complexity * of: * * O(nm log n), n := nr_cpus, m := nr_tasks (8) * * * WORK CONSERVING * * In order to avoid CPUs going idle while there's still work to do, new idle * balancing is more aggressive and has the newly idle CPU iterate up the domain * tree itself instead of relying on other CPUs to bring it work. * * This adds some complexity to both (5) and (8) but it reduces the total idle * time. * * [XXX more?] * * * CGROUPS * * Cgroups make a horror show out of (2), instead of a simple sum we get: * * s_k,i * W_i,0 = \Sum_j \Prod_k w_k * ----- (9) * S_k * * Where * * s_k,i = \Sum_j w_i,j,k and S_k = \Sum_i s_k,i (10) * * w_i,j,k is the weight of the j-th runnable task in the k-th cgroup on CPU i. * * The big problem is S_k, its a global sum needed to compute a local (W_i) * property. * * [XXX write more on how we solve this.. _after_ merging pjt's patches that * rewrite all of this once again.] */ static unsigned long __read_mostly max_load_balance_interval = HZ/10; enum fbq_type { regular, remote, all }; /* * 'group_type' describes the group of CPUs at the moment of load balancing. * * The enum is ordered by pulling priority, with the group with lowest priority * first so the group_type can simply be compared when selecting the busiest * group. See update_sd_pick_busiest(). */ enum group_type { /* The group has spare capacity that can be used to run more tasks. */ group_has_spare = 0, /* * The group is fully used and the tasks don't compete for more CPU * cycles. Nevertheless, some tasks might wait before running. */ group_fully_busy, /* * One task doesn't fit with CPU's capacity and must be migrated to a * more powerful CPU. */ group_misfit_task, /* * Balance SMT group that's fully busy. Can benefit from migration * a task on SMT with busy sibling to another CPU on idle core. */ group_smt_balance, /* * SD_ASYM_PACKING only: One local CPU with higher capacity is available, * and the task should be migrated to it instead of running on the * current CPU. */ group_asym_packing, /* * The tasks' affinity constraints previously prevented the scheduler * from balancing the load across the system. */ group_imbalanced, /* * The CPU is overloaded and can't provide expected CPU cycles to all * tasks. */ group_overloaded }; enum migration_type { migrate_load = 0, migrate_util, migrate_task, migrate_misfit }; #define LBF_ALL_PINNED 0x01 #define LBF_NEED_BREAK 0x02 #define LBF_DST_PINNED 0x04 #define LBF_SOME_PINNED 0x08 #define LBF_ACTIVE_LB 0x10 struct lb_env { struct sched_domain *sd; struct rq *src_rq; int src_cpu; int dst_cpu; struct rq *dst_rq; struct cpumask *dst_grpmask; int new_dst_cpu; enum cpu_idle_type idle; long imbalance; /* The set of CPUs under consideration for load-balancing */ struct cpumask *cpus; unsigned int flags; unsigned int loop; unsigned int loop_break; unsigned int loop_max; enum fbq_type fbq_type; enum migration_type migration_type; struct list_head tasks; }; /* * Is this task likely cache-hot: */ static int task_hot(struct task_struct *p, struct lb_env *env) { s64 delta; lockdep_assert_rq_held(env->src_rq); if (p->sched_class != &fair_sched_class) return 0; if (unlikely(task_has_idle_policy(p))) return 0; /* SMT siblings share cache */ if (env->sd->flags & SD_SHARE_CPUCAPACITY) return 0; /* * Buddy candidates are cache hot: */ if (sched_feat(CACHE_HOT_BUDDY) && env->dst_rq->nr_running && (&p->se == cfs_rq_of(&p->se)->next)) return 1; if (sysctl_sched_migration_cost == -1) return 1; /* * Don't migrate task if the task's cookie does not match * with the destination CPU's core cookie. */ if (!sched_core_cookie_match(cpu_rq(env->dst_cpu), p)) return 1; if (sysctl_sched_migration_cost == 0) return 0; delta = rq_clock_task(env->src_rq) - p->se.exec_start; return delta < (s64)sysctl_sched_migration_cost; } #ifdef CONFIG_NUMA_BALANCING /* * Returns 1, if task migration degrades locality * Returns 0, if task migration improves locality i.e migration preferred. * Returns -1, if task migration is not affected by locality. */ static int migrate_degrades_locality(struct task_struct *p, struct lb_env *env) { struct numa_group *numa_group = rcu_dereference(p->numa_group); unsigned long src_weight, dst_weight; int src_nid, dst_nid, dist; if (!static_branch_likely(&sched_numa_balancing)) return -1; if (!p->numa_faults || !(env->sd->flags & SD_NUMA)) return -1; src_nid = cpu_to_node(env->src_cpu); dst_nid = cpu_to_node(env->dst_cpu); if (src_nid == dst_nid) return -1; /* Migrating away from the preferred node is always bad. */ if (src_nid == p->numa_preferred_nid) { if (env->src_rq->nr_running > env->src_rq->nr_preferred_running) return 1; else return -1; } /* Encourage migration to the preferred node. */ if (dst_nid == p->numa_preferred_nid) return 0; /* Leaving a core idle is often worse than degrading locality. */ if (env->idle == CPU_IDLE) return -1; dist = node_distance(src_nid, dst_nid); if (numa_group) { src_weight = group_weight(p, src_nid, dist); dst_weight = group_weight(p, dst_nid, dist); } else { src_weight = task_weight(p, src_nid, dist); dst_weight = task_weight(p, dst_nid, dist); } return dst_weight < src_weight; } #else static inline int migrate_degrades_locality(struct task_struct *p, struct lb_env *env) { return -1; } #endif /* * can_migrate_task - may task p from runqueue rq be migrated to this_cpu? */ static int can_migrate_task(struct task_struct *p, struct lb_env *env) { int tsk_cache_hot; lockdep_assert_rq_held(env->src_rq); /* * We do not migrate tasks that are: * 1) throttled_lb_pair, or * 2) cannot be migrated to this CPU due to cpus_ptr, or * 3) running (obviously), or * 4) are cache-hot on their current CPU. */ if (throttled_lb_pair(task_group(p), env->src_cpu, env->dst_cpu)) return 0; /* Disregard pcpu kthreads; they are where they need to be. */ if (kthread_is_per_cpu(p)) return 0; if (!cpumask_test_cpu(env->dst_cpu, p->cpus_ptr)) { int cpu; schedstat_inc(p->stats.nr_failed_migrations_affine); env->flags |= LBF_SOME_PINNED; /* * Remember if this task can be migrated to any other CPU in * our sched_group. We may want to revisit it if we couldn't * meet load balance goals by pulling other tasks on src_cpu. * * Avoid computing new_dst_cpu * - for NEWLY_IDLE * - if we have already computed one in current iteration * - if it's an active balance */ if (env->idle == CPU_NEWLY_IDLE || env->flags & (LBF_DST_PINNED | LBF_ACTIVE_LB)) return 0; /* Prevent to re-select dst_cpu via env's CPUs: */ for_each_cpu_and(cpu, env->dst_grpmask, env->cpus) { if (cpumask_test_cpu(cpu, p->cpus_ptr)) { env->flags |= LBF_DST_PINNED; env->new_dst_cpu = cpu; break; } } return 0; } /* Record that we found at least one task that could run on dst_cpu */ env->flags &= ~LBF_ALL_PINNED; if (task_on_cpu(env->src_rq, p)) { schedstat_inc(p->stats.nr_failed_migrations_running); return 0; } /* * Aggressive migration if: * 1) active balance * 2) destination numa is preferred * 3) task is cache cold, or * 4) too many balance attempts have failed. */ if (env->flags & LBF_ACTIVE_LB) return 1; tsk_cache_hot = migrate_degrades_locality(p, env); if (tsk_cache_hot == -1) tsk_cache_hot = task_hot(p, env); if (tsk_cache_hot <= 0 || env->sd->nr_balance_failed > env->sd->cache_nice_tries) { if (tsk_cache_hot == 1) { schedstat_inc(env->sd->lb_hot_gained[env->idle]); schedstat_inc(p->stats.nr_forced_migrations); } return 1; } schedstat_inc(p->stats.nr_failed_migrations_hot); return 0; } /* * detach_task() -- detach the task for the migration specified in env */ static void detach_task(struct task_struct *p, struct lb_env *env) { lockdep_assert_rq_held(env->src_rq); deactivate_task(env->src_rq, p, DEQUEUE_NOCLOCK); set_task_cpu(p, env->dst_cpu); } /* * detach_one_task() -- tries to dequeue exactly one task from env->src_rq, as * part of active balancing operations within "domain". * * Returns a task if successful and NULL otherwise. */ static struct task_struct *detach_one_task(struct lb_env *env) { struct task_struct *p; lockdep_assert_rq_held(env->src_rq); list_for_each_entry_reverse(p, &env->src_rq->cfs_tasks, se.group_node) { if (!can_migrate_task(p, env)) continue; detach_task(p, env); /* * Right now, this is only the second place where * lb_gained[env->idle] is updated (other is detach_tasks) * so we can safely collect stats here rather than * inside detach_tasks(). */ schedstat_inc(env->sd->lb_gained[env->idle]); return p; } return NULL; } /* * detach_tasks() -- tries to detach up to imbalance load/util/tasks from * busiest_rq, as part of a balancing operation within domain "sd". * * Returns number of detached tasks if successful and 0 otherwise. */ static int detach_tasks(struct lb_env *env) { struct list_head *tasks = &env->src_rq->cfs_tasks; unsigned long util, load; struct task_struct *p; int detached = 0; lockdep_assert_rq_held(env->src_rq); /* * Source run queue has been emptied by another CPU, clear * LBF_ALL_PINNED flag as we will not test any task. */ if (env->src_rq->nr_running <= 1) { env->flags &= ~LBF_ALL_PINNED; return 0; } if (env->imbalance <= 0) return 0; while (!list_empty(tasks)) { /* * We don't want to steal all, otherwise we may be treated likewise, * which could at worst lead to a livelock crash. */ if (env->idle != CPU_NOT_IDLE && env->src_rq->nr_running <= 1) break; env->loop++; /* * We've more or less seen every task there is, call it quits * unless we haven't found any movable task yet. */ if (env->loop > env->loop_max && !(env->flags & LBF_ALL_PINNED)) break; /* take a breather every nr_migrate tasks */ if (env->loop > env->loop_break) { env->loop_break += SCHED_NR_MIGRATE_BREAK; env->flags |= LBF_NEED_BREAK; break; } p = list_last_entry(tasks, struct task_struct, se.group_node); if (!can_migrate_task(p, env)) goto next; switch (env->migration_type) { case migrate_load: /* * Depending of the number of CPUs and tasks and the * cgroup hierarchy, task_h_load() can return a null * value. Make sure that env->imbalance decreases * otherwise detach_tasks() will stop only after * detaching up to loop_max tasks. */ load = max_t(unsigned long, task_h_load(p), 1); if (sched_feat(LB_MIN) && load < 16 && !env->sd->nr_balance_failed) goto next; /* * Make sure that we don't migrate too much load. * Nevertheless, let relax the constraint if * scheduler fails to find a good waiting task to * migrate. */ if (shr_bound(load, env->sd->nr_balance_failed) > env->imbalance) goto next; env->imbalance -= load; break; case migrate_util: util = task_util_est(p); if (util > env->imbalance) goto next; env->imbalance -= util; break; case migrate_task: env->imbalance--; break; case migrate_misfit: /* This is not a misfit task */ if (task_fits_cpu(p, env->src_cpu)) goto next; env->imbalance = 0; break; } detach_task(p, env); list_add(&p->se.group_node, &env->tasks); detached++; #ifdef CONFIG_PREEMPTION /* * NEWIDLE balancing is a source of latency, so preemptible * kernels will stop after the first task is detached to minimize * the critical section. */ if (env->idle == CPU_NEWLY_IDLE) break; #endif /* * We only want to steal up to the prescribed amount of * load/util/tasks. */ if (env->imbalance <= 0) break; continue; next: list_move(&p->se.group_node, tasks); } /* * Right now, this is one of only two places we collect this stat * so we can safely collect detach_one_task() stats here rather * than inside detach_one_task(). */ schedstat_add(env->sd->lb_gained[env->idle], detached); return detached; } /* * attach_task() -- attach the task detached by detach_task() to its new rq. */ static void attach_task(struct rq *rq, struct task_struct *p) { lockdep_assert_rq_held(rq); WARN_ON_ONCE(task_rq(p) != rq); activate_task(rq, p, ENQUEUE_NOCLOCK); wakeup_preempt(rq, p, 0); } /* * attach_one_task() -- attaches the task returned from detach_one_task() to * its new rq. */ static void attach_one_task(struct rq *rq, struct task_struct *p) { struct rq_flags rf; rq_lock(rq, &rf); update_rq_clock(rq); attach_task(rq, p); rq_unlock(rq, &rf); } /* * attach_tasks() -- attaches all tasks detached by detach_tasks() to their * new rq. */ static void attach_tasks(struct lb_env *env) { struct list_head *tasks = &env->tasks; struct task_struct *p; struct rq_flags rf; rq_lock(env->dst_rq, &rf); update_rq_clock(env->dst_rq); while (!list_empty(tasks)) { p = list_first_entry(tasks, struct task_struct, se.group_node); list_del_init(&p->se.group_node); attach_task(env->dst_rq, p); } rq_unlock(env->dst_rq, &rf); } #ifdef CONFIG_NO_HZ_COMMON static inline bool cfs_rq_has_blocked(struct cfs_rq *cfs_rq) { if (cfs_rq->avg.load_avg) return true; if (cfs_rq->avg.util_avg) return true; return false; } static inline bool others_have_blocked(struct rq *rq) { if (READ_ONCE(rq->avg_rt.util_avg)) return true; if (READ_ONCE(rq->avg_dl.util_avg)) return true; if (thermal_load_avg(rq)) return true; #ifdef CONFIG_HAVE_SCHED_AVG_IRQ if (READ_ONCE(rq->avg_irq.util_avg)) return true; #endif return false; } static inline void update_blocked_load_tick(struct rq *rq) { WRITE_ONCE(rq->last_blocked_load_update_tick, jiffies); } static inline void update_blocked_load_status(struct rq *rq, bool has_blocked) { if (!has_blocked) rq->has_blocked_load = 0; } #else static inline bool cfs_rq_has_blocked(struct cfs_rq *cfs_rq) { return false; } static inline bool others_have_blocked(struct rq *rq) { return false; } static inline void update_blocked_load_tick(struct rq *rq) {} static inline void update_blocked_load_status(struct rq *rq, bool has_blocked) {} #endif static bool __update_blocked_others(struct rq *rq, bool *done) { const struct sched_class *curr_class; u64 now = rq_clock_pelt(rq); unsigned long thermal_pressure; bool decayed; /* * update_load_avg() can call cpufreq_update_util(). Make sure that RT, * DL and IRQ signals have been updated before updating CFS. */ curr_class = rq->curr->sched_class; thermal_pressure = arch_scale_thermal_pressure(cpu_of(rq)); decayed = update_rt_rq_load_avg(now, rq, curr_class == &rt_sched_class) | update_dl_rq_load_avg(now, rq, curr_class == &dl_sched_class) | update_thermal_load_avg(rq_clock_thermal(rq), rq, thermal_pressure) | update_irq_load_avg(rq, 0); if (others_have_blocked(rq)) *done = false; return decayed; } #ifdef CONFIG_FAIR_GROUP_SCHED static bool __update_blocked_fair(struct rq *rq, bool *done) { struct cfs_rq *cfs_rq, *pos; bool decayed = false; int cpu = cpu_of(rq); /* * Iterates the task_group tree in a bottom up fashion, see * list_add_leaf_cfs_rq() for details. */ for_each_leaf_cfs_rq_safe(rq, cfs_rq, pos) { struct sched_entity *se; if (update_cfs_rq_load_avg(cfs_rq_clock_pelt(cfs_rq), cfs_rq)) { update_tg_load_avg(cfs_rq); if (cfs_rq->nr_running == 0) update_idle_cfs_rq_clock_pelt(cfs_rq); if (cfs_rq == &rq->cfs) decayed = true; } /* Propagate pending load changes to the parent, if any: */ se = cfs_rq->tg->se[cpu]; if (se && !skip_blocked_update(se)) update_load_avg(cfs_rq_of(se), se, UPDATE_TG); /* * There can be a lot of idle CPU cgroups. Don't let fully * decayed cfs_rqs linger on the list. */ if (cfs_rq_is_decayed(cfs_rq)) list_del_leaf_cfs_rq(cfs_rq); /* Don't need periodic decay once load/util_avg are null */ if (cfs_rq_has_blocked(cfs_rq)) *done = false; } return decayed; } /* * Compute the hierarchical load factor for cfs_rq and all its ascendants. * This needs to be done in a top-down fashion because the load of a child * group is a fraction of its parents load. */ static void update_cfs_rq_h_load(struct cfs_rq *cfs_rq) { struct rq *rq = rq_of(cfs_rq); struct sched_entity *se = cfs_rq->tg->se[cpu_of(rq)]; unsigned long now = jiffies; unsigned long load; if (cfs_rq->last_h_load_update == now) return; WRITE_ONCE(cfs_rq->h_load_next, NULL); for_each_sched_entity(se) { cfs_rq = cfs_rq_of(se); WRITE_ONCE(cfs_rq->h_load_next, se); if (cfs_rq->last_h_load_update == now) break; } if (!se) { cfs_rq->h_load = cfs_rq_load_avg(cfs_rq); cfs_rq->last_h_load_update = now; } while ((se = READ_ONCE(cfs_rq->h_load_next)) != NULL) { load = cfs_rq->h_load; load = div64_ul(load * se->avg.load_avg, cfs_rq_load_avg(cfs_rq) + 1); cfs_rq = group_cfs_rq(se); cfs_rq->h_load = load; cfs_rq->last_h_load_update = now; } } static unsigned long task_h_load(struct task_struct *p) { struct cfs_rq *cfs_rq = task_cfs_rq(p); update_cfs_rq_h_load(cfs_rq); return div64_ul(p->se.avg.load_avg * cfs_rq->h_load, cfs_rq_load_avg(cfs_rq) + 1); } #else static bool __update_blocked_fair(struct rq *rq, bool *done) { struct cfs_rq *cfs_rq = &rq->cfs; bool decayed; decayed = update_cfs_rq_load_avg(cfs_rq_clock_pelt(cfs_rq), cfs_rq); if (cfs_rq_has_blocked(cfs_rq)) *done = false; return decayed; } static unsigned long task_h_load(struct task_struct *p) { return p->se.avg.load_avg; } #endif static void update_blocked_averages(int cpu) { bool decayed = false, done = true; struct rq *rq = cpu_rq(cpu); struct rq_flags rf; rq_lock_irqsave(rq, &rf); update_blocked_load_tick(rq); update_rq_clock(rq); decayed |= __update_blocked_others(rq, &done); decayed |= __update_blocked_fair(rq, &done); update_blocked_load_status(rq, !done); if (decayed) cpufreq_update_util(rq, 0); rq_unlock_irqrestore(rq, &rf); } /********** Helpers for find_busiest_group ************************/ /* * sg_lb_stats - stats of a sched_group required for load_balancing */ struct sg_lb_stats { unsigned long avg_load; /*Avg load across the CPUs of the group */ unsigned long group_load; /* Total load over the CPUs of the group */ unsigned long group_capacity; unsigned long group_util; /* Total utilization over the CPUs of the group */ unsigned long group_runnable; /* Total runnable time over the CPUs of the group */ unsigned int sum_nr_running; /* Nr of tasks running in the group */ unsigned int sum_h_nr_running; /* Nr of CFS tasks running in the group */ unsigned int idle_cpus; unsigned int group_weight; enum group_type group_type; unsigned int group_asym_packing; /* Tasks should be moved to preferred CPU */ unsigned int group_smt_balance; /* Task on busy SMT be moved */ unsigned long group_misfit_task_load; /* A CPU has a task too big for its capacity */ #ifdef CONFIG_NUMA_BALANCING unsigned int nr_numa_running; unsigned int nr_preferred_running; #endif }; /* * sd_lb_stats - Structure to store the statistics of a sched_domain * during load balancing. */ struct sd_lb_stats { struct sched_group *busiest; /* Busiest group in this sd */ struct sched_group *local; /* Local group in this sd */ unsigned long total_load; /* Total load of all groups in sd */ unsigned long total_capacity; /* Total capacity of all groups in sd */ unsigned long avg_load; /* Average load across all groups in sd */ unsigned int prefer_sibling; /* tasks should go to sibling first */ struct sg_lb_stats busiest_stat;/* Statistics of the busiest group */ struct sg_lb_stats local_stat; /* Statistics of the local group */ }; static inline void init_sd_lb_stats(struct sd_lb_stats *sds) { /* * Skimp on the clearing to avoid duplicate work. We can avoid clearing * local_stat because update_sg_lb_stats() does a full clear/assignment. * We must however set busiest_stat::group_type and * busiest_stat::idle_cpus to the worst busiest group because * update_sd_pick_busiest() reads these before assignment. */ *sds = (struct sd_lb_stats){ .busiest = NULL, .local = NULL, .total_load = 0UL, .total_capacity = 0UL, .busiest_stat = { .idle_cpus = UINT_MAX, .group_type = group_has_spare, }, }; } static unsigned long scale_rt_capacity(int cpu) { struct rq *rq = cpu_rq(cpu); unsigned long max = arch_scale_cpu_capacity(cpu); unsigned long used, free; unsigned long irq; irq = cpu_util_irq(rq); if (unlikely(irq >= max)) return 1; /* * avg_rt.util_avg and avg_dl.util_avg track binary signals * (running and not running) with weights 0 and 1024 respectively. * avg_thermal.load_avg tracks thermal pressure and the weighted * average uses the actual delta max capacity(load). */ used = READ_ONCE(rq->avg_rt.util_avg); used += READ_ONCE(rq->avg_dl.util_avg); used += thermal_load_avg(rq); if (unlikely(used >= max)) return 1; free = max - used; return scale_irq_capacity(free, irq, max); } static void update_cpu_capacity(struct sched_domain *sd, int cpu) { unsigned long capacity = scale_rt_capacity(cpu); struct sched_group *sdg = sd->groups; if (!capacity) capacity = 1; cpu_rq(cpu)->cpu_capacity = capacity; trace_sched_cpu_capacity_tp(cpu_rq(cpu)); sdg->sgc->capacity = capacity; sdg->sgc->min_capacity = capacity; sdg->sgc->max_capacity = capacity; } void update_group_capacity(struct sched_domain *sd, int cpu) { struct sched_domain *child = sd->child; struct sched_group *group, *sdg = sd->groups; unsigned long capacity, min_capacity, max_capacity; unsigned long interval; interval = msecs_to_jiffies(sd->balance_interval); interval = clamp(interval, 1UL, max_load_balance_interval); sdg->sgc->next_update = jiffies + interval; if (!child) { update_cpu_capacity(sd, cpu); return; } capacity = 0; min_capacity = ULONG_MAX; max_capacity = 0; if (child->flags & SD_OVERLAP) { /* * SD_OVERLAP domains cannot assume that child groups * span the current group. */ for_each_cpu(cpu, sched_group_span(sdg)) { unsigned long cpu_cap = capacity_of(cpu); capacity += cpu_cap; min_capacity = min(cpu_cap, min_capacity); max_capacity = max(cpu_cap, max_capacity); } } else { /* * !SD_OVERLAP domains can assume that child groups * span the current group. */ group = child->groups; do { struct sched_group_capacity *sgc = group->sgc; capacity += sgc->capacity; min_capacity = min(sgc->min_capacity, min_capacity); max_capacity = max(sgc->max_capacity, max_capacity); group = group->next; } while (group != child->groups); } sdg->sgc->capacity = capacity; sdg->sgc->min_capacity = min_capacity; sdg->sgc->max_capacity = max_capacity; } /* * Check whether the capacity of the rq has been noticeably reduced by side * activity. The imbalance_pct is used for the threshold. * Return true is the capacity is reduced */ static inline int check_cpu_capacity(struct rq *rq, struct sched_domain *sd) { return ((rq->cpu_capacity * sd->imbalance_pct) < (arch_scale_cpu_capacity(cpu_of(rq)) * 100)); } /* * Check whether a rq has a misfit task and if it looks like we can actually * help that task: we can migrate the task to a CPU of higher capacity, or * the task's current CPU is heavily pressured. */ static inline int check_misfit_status(struct rq *rq, struct sched_domain *sd) { return rq->misfit_task_load && (arch_scale_cpu_capacity(rq->cpu) < rq->rd->max_cpu_capacity || check_cpu_capacity(rq, sd)); } /* * Group imbalance indicates (and tries to solve) the problem where balancing * groups is inadequate due to ->cpus_ptr constraints. * * Imagine a situation of two groups of 4 CPUs each and 4 tasks each with a * cpumask covering 1 CPU of the first group and 3 CPUs of the second group. * Something like: * * { 0 1 2 3 } { 4 5 6 7 } * * * * * * * If we were to balance group-wise we'd place two tasks in the first group and * two tasks in the second group. Clearly this is undesired as it will overload * cpu 3 and leave one of the CPUs in the second group unused. * * The current solution to this issue is detecting the skew in the first group * by noticing the lower domain failed to reach balance and had difficulty * moving tasks due to affinity constraints. * * When this is so detected; this group becomes a candidate for busiest; see * update_sd_pick_busiest(). And calculate_imbalance() and * find_busiest_group() avoid some of the usual balance conditions to allow it * to create an effective group imbalance. * * This is a somewhat tricky proposition since the next run might not find the * group imbalance and decide the groups need to be balanced again. A most * subtle and fragile situation. */ static inline int sg_imbalanced(struct sched_group *group) { return group->sgc->imbalance; } /* * group_has_capacity returns true if the group has spare capacity that could * be used by some tasks. * We consider that a group has spare capacity if the number of task is * smaller than the number of CPUs or if the utilization is lower than the * available capacity for CFS tasks. * For the latter, we use a threshold to stabilize the state, to take into * account the variance of the tasks' load and to return true if the available * capacity in meaningful for the load balancer. * As an example, an available capacity of 1% can appear but it doesn't make * any benefit for the load balance. */ static inline bool group_has_capacity(unsigned int imbalance_pct, struct sg_lb_stats *sgs) { if (sgs->sum_nr_running < sgs->group_weight) return true; if ((sgs->group_capacity * imbalance_pct) < (sgs->group_runnable * 100)) return false; if ((sgs->group_capacity * 100) > (sgs->group_util * imbalance_pct)) return true; return false; } /* * group_is_overloaded returns true if the group has more tasks than it can * handle. * group_is_overloaded is not equals to !group_has_capacity because a group * with the exact right number of tasks, has no more spare capacity but is not * overloaded so both group_has_capacity and group_is_overloaded return * false. */ static inline bool group_is_overloaded(unsigned int imbalance_pct, struct sg_lb_stats *sgs) { if (sgs->sum_nr_running <= sgs->group_weight) return false; if ((sgs->group_capacity * 100) < (sgs->group_util * imbalance_pct)) return true; if ((sgs->group_capacity * imbalance_pct) < (sgs->group_runnable * 100)) return true; return false; } static inline enum group_type group_classify(unsigned int imbalance_pct, struct sched_group *group, struct sg_lb_stats *sgs) { if (group_is_overloaded(imbalance_pct, sgs)) return group_overloaded; if (sg_imbalanced(group)) return group_imbalanced; if (sgs->group_asym_packing) return group_asym_packing; if (sgs->group_smt_balance) return group_smt_balance; if (sgs->group_misfit_task_load) return group_misfit_task; if (!group_has_capacity(imbalance_pct, sgs)) return group_fully_busy; return group_has_spare; } /** * sched_use_asym_prio - Check whether asym_packing priority must be used * @sd: The scheduling domain of the load balancing * @cpu: A CPU * * Always use CPU priority when balancing load between SMT siblings. When * balancing load between cores, it is not sufficient that @cpu is idle. Only * use CPU priority if the whole core is idle. * * Returns: True if the priority of @cpu must be followed. False otherwise. */ static bool sched_use_asym_prio(struct sched_domain *sd, int cpu) { if (!sched_smt_active()) return true; return sd->flags & SD_SHARE_CPUCAPACITY || is_core_idle(cpu); } /** * sched_asym - Check if the destination CPU can do asym_packing load balance * @env: The load balancing environment * @sds: Load-balancing data with statistics of the local group * @sgs: Load-balancing statistics of the candidate busiest group * @group: The candidate busiest group * * @env::dst_cpu can do asym_packing if it has higher priority than the * preferred CPU of @group. * * SMT is a special case. If we are balancing load between cores, @env::dst_cpu * can do asym_packing balance only if all its SMT siblings are idle. Also, it * can only do it if @group is an SMT group and has exactly on busy CPU. Larger * imbalances in the number of CPUS are dealt with in find_busiest_group(). * * If we are balancing load within an SMT core, or at PKG domain level, always * proceed. * * Return: true if @env::dst_cpu can do with asym_packing load balance. False * otherwise. */ static inline bool sched_asym(struct lb_env *env, struct sd_lb_stats *sds, struct sg_lb_stats *sgs, struct sched_group *group) { /* Ensure that the whole local core is idle, if applicable. */ if (!sched_use_asym_prio(env->sd, env->dst_cpu)) return false; /* * CPU priorities does not make sense for SMT cores with more than one * busy sibling. */ if (group->flags & SD_SHARE_CPUCAPACITY) { if (sgs->group_weight - sgs->idle_cpus != 1) return false; } return sched_asym_prefer(env->dst_cpu, group->asym_prefer_cpu); } /* One group has more than one SMT CPU while the other group does not */ static inline bool smt_vs_nonsmt_groups(struct sched_group *sg1, struct sched_group *sg2) { if (!sg1 || !sg2) return false; return (sg1->flags & SD_SHARE_CPUCAPACITY) != (sg2->flags & SD_SHARE_CPUCAPACITY); } static inline bool smt_balance(struct lb_env *env, struct sg_lb_stats *sgs, struct sched_group *group) { if (env->idle == CPU_NOT_IDLE) return false; /* * For SMT source group, it is better to move a task * to a CPU that doesn't have multiple tasks sharing its CPU capacity. * Note that if a group has a single SMT, SD_SHARE_CPUCAPACITY * will not be on. */ if (group->flags & SD_SHARE_CPUCAPACITY && sgs->sum_h_nr_running > 1) return true; return false; } static inline long sibling_imbalance(struct lb_env *env, struct sd_lb_stats *sds, struct sg_lb_stats *busiest, struct sg_lb_stats *local) { int ncores_busiest, ncores_local; long imbalance; if (env->idle == CPU_NOT_IDLE || !busiest->sum_nr_running) return 0; ncores_busiest = sds->busiest->cores; ncores_local = sds->local->cores; if (ncores_busiest == ncores_local) { imbalance = busiest->sum_nr_running; lsub_positive(&imbalance, local->sum_nr_running); return imbalance; } /* Balance such that nr_running/ncores ratio are same on both groups */ imbalance = ncores_local * busiest->sum_nr_running; lsub_positive(&imbalance, ncores_busiest * local->sum_nr_running); /* Normalize imbalance and do rounding on normalization */ imbalance = 2 * imbalance + ncores_local + ncores_busiest; imbalance /= ncores_local + ncores_busiest; /* Take advantage of resource in an empty sched group */ if (imbalance <= 1 && local->sum_nr_running == 0 && busiest->sum_nr_running > 1) imbalance = 2; return imbalance; } static inline bool sched_reduced_capacity(struct rq *rq, struct sched_domain *sd) { /* * When there is more than 1 task, the group_overloaded case already * takes care of cpu with reduced capacity */ if (rq->cfs.h_nr_running != 1) return false; return check_cpu_capacity(rq, sd); } /** * update_sg_lb_stats - Update sched_group's statistics for load balancing. * @env: The load balancing environment. * @sds: Load-balancing data with statistics of the local group. * @group: sched_group whose statistics are to be updated. * @sgs: variable to hold the statistics for this group. * @sg_status: Holds flag indicating the status of the sched_group */ static inline void update_sg_lb_stats(struct lb_env *env, struct sd_lb_stats *sds, struct sched_group *group, struct sg_lb_stats *sgs, int *sg_status) { int i, nr_running, local_group; memset(sgs, 0, sizeof(*sgs)); local_group = group == sds->local; for_each_cpu_and(i, sched_group_span(group), env->cpus) { struct rq *rq = cpu_rq(i); unsigned long load = cpu_load(rq); sgs->group_load += load; sgs->group_util += cpu_util_cfs(i); sgs->group_runnable += cpu_runnable(rq); sgs->sum_h_nr_running += rq->cfs.h_nr_running; nr_running = rq->nr_running; sgs->sum_nr_running += nr_running; if (nr_running > 1) *sg_status |= SG_OVERLOAD; if (cpu_overutilized(i)) *sg_status |= SG_OVERUTILIZED; #ifdef CONFIG_NUMA_BALANCING sgs->nr_numa_running += rq->nr_numa_running; sgs->nr_preferred_running += rq->nr_preferred_running; #endif /* * No need to call idle_cpu() if nr_running is not 0 */ if (!nr_running && idle_cpu(i)) { sgs->idle_cpus++; /* Idle cpu can't have misfit task */ continue; } if (local_group) continue; if (env->sd->flags & SD_ASYM_CPUCAPACITY) { /* Check for a misfit task on the cpu */ if (sgs->group_misfit_task_load < rq->misfit_task_load) { sgs->group_misfit_task_load = rq->misfit_task_load; *sg_status |= SG_OVERLOAD; } } else if ((env->idle != CPU_NOT_IDLE) && sched_reduced_capacity(rq, env->sd)) { /* Check for a task running on a CPU with reduced capacity */ if (sgs->group_misfit_task_load < load) sgs->group_misfit_task_load = load; } } sgs->group_capacity = group->sgc->capacity; sgs->group_weight = group->group_weight; /* Check if dst CPU is idle and preferred to this group */ if (!local_group && env->sd->flags & SD_ASYM_PACKING && env->idle != CPU_NOT_IDLE && sgs->sum_h_nr_running && sched_asym(env, sds, sgs, group)) { sgs->group_asym_packing = 1; } /* Check for loaded SMT group to be balanced to dst CPU */ if (!local_group && smt_balance(env, sgs, group)) sgs->group_smt_balance = 1; sgs->group_type = group_classify(env->sd->imbalance_pct, group, sgs); /* Computing avg_load makes sense only when group is overloaded */ if (sgs->group_type == group_overloaded) sgs->avg_load = (sgs->group_load * SCHED_CAPACITY_SCALE) / sgs->group_capacity; } /** * update_sd_pick_busiest - return 1 on busiest group * @env: The load balancing environment. * @sds: sched_domain statistics * @sg: sched_group candidate to be checked for being the busiest * @sgs: sched_group statistics * * Determine if @sg is a busier group than the previously selected * busiest group. * * Return: %true if @sg is a busier group than the previously selected * busiest group. %false otherwise. */ static bool update_sd_pick_busiest(struct lb_env *env, struct sd_lb_stats *sds, struct sched_group *sg, struct sg_lb_stats *sgs) { struct sg_lb_stats *busiest = &sds->busiest_stat; /* Make sure that there is at least one task to pull */ if (!sgs->sum_h_nr_running) return false; /* * Don't try to pull misfit tasks we can't help. * We can use max_capacity here as reduction in capacity on some * CPUs in the group should either be possible to resolve * internally or be covered by avg_load imbalance (eventually). */ if ((env->sd->flags & SD_ASYM_CPUCAPACITY) && (sgs->group_type == group_misfit_task) && (!capacity_greater(capacity_of(env->dst_cpu), sg->sgc->max_capacity) || sds->local_stat.group_type != group_has_spare)) return false; if (sgs->group_type > busiest->group_type) return true; if (sgs->group_type < busiest->group_type) return false; /* * The candidate and the current busiest group are the same type of * group. Let check which one is the busiest according to the type. */ switch (sgs->group_type) { case group_overloaded: /* Select the overloaded group with highest avg_load. */ if (sgs->avg_load <= busiest->avg_load) return false; break; case group_imbalanced: /* * Select the 1st imbalanced group as we don't have any way to * choose one more than another. */ return false; case group_asym_packing: /* Prefer to move from lowest priority CPU's work */ if (sched_asym_prefer(sg->asym_prefer_cpu, sds->busiest->asym_prefer_cpu)) return false; break; case group_misfit_task: /* * If we have more than one misfit sg go with the biggest * misfit. */ if (sgs->group_misfit_task_load < busiest->group_misfit_task_load) return false; break; case group_smt_balance: /* * Check if we have spare CPUs on either SMT group to * choose has spare or fully busy handling. */ if (sgs->idle_cpus != 0 || busiest->idle_cpus != 0) goto has_spare; fallthrough; case group_fully_busy: /* * Select the fully busy group with highest avg_load. In * theory, there is no need to pull task from such kind of * group because tasks have all compute capacity that they need * but we can still improve the overall throughput by reducing * contention when accessing shared HW resources. * * XXX for now avg_load is not computed and always 0 so we * select the 1st one, except if @sg is composed of SMT * siblings. */ if (sgs->avg_load < busiest->avg_load) return false; if (sgs->avg_load == busiest->avg_load) { /* * SMT sched groups need more help than non-SMT groups. * If @sg happens to also be SMT, either choice is good. */ if (sds->busiest->flags & SD_SHARE_CPUCAPACITY) return false; } break; case group_has_spare: /* * Do not pick sg with SMT CPUs over sg with pure CPUs, * as we do not want to pull task off SMT core with one task * and make the core idle. */ if (smt_vs_nonsmt_groups(sds->busiest, sg)) { if (sg->flags & SD_SHARE_CPUCAPACITY && sgs->sum_h_nr_running <= 1) return false; else return true; } has_spare: /* * Select not overloaded group with lowest number of idle cpus * and highest number of running tasks. We could also compare * the spare capacity which is more stable but it can end up * that the group has less spare capacity but finally more idle * CPUs which means less opportunity to pull tasks. */ if (sgs->idle_cpus > busiest->idle_cpus) return false; else if ((sgs->idle_cpus == busiest->idle_cpus) && (sgs->sum_nr_running <= busiest->sum_nr_running)) return false; break; } /* * Candidate sg has no more than one task per CPU and has higher * per-CPU capacity. Migrating tasks to less capable CPUs may harm * throughput. Maximize throughput, power/energy consequences are not * considered. */ if ((env->sd->flags & SD_ASYM_CPUCAPACITY) && (sgs->group_type <= group_fully_busy) && (capacity_greater(sg->sgc->min_capacity, capacity_of(env->dst_cpu)))) return false; return true; } #ifdef CONFIG_NUMA_BALANCING static inline enum fbq_type fbq_classify_group(struct sg_lb_stats *sgs) { if (sgs->sum_h_nr_running > sgs->nr_numa_running) return regular; if (sgs->sum_h_nr_running > sgs->nr_preferred_running) return remote; return all; } static inline enum fbq_type fbq_classify_rq(struct rq *rq) { if (rq->nr_running > rq->nr_numa_running) return regular; if (rq->nr_running > rq->nr_preferred_running) return remote; return all; } #else static inline enum fbq_type fbq_classify_group(struct sg_lb_stats *sgs) { return all; } static inline enum fbq_type fbq_classify_rq(struct rq *rq) { return regular; } #endif /* CONFIG_NUMA_BALANCING */ struct sg_lb_stats; /* * task_running_on_cpu - return 1 if @p is running on @cpu. */ static unsigned int task_running_on_cpu(int cpu, struct task_struct *p) { /* Task has no contribution or is new */ if (cpu != task_cpu(p) || !READ_ONCE(p->se.avg.last_update_time)) return 0; if (task_on_rq_queued(p)) return 1; return 0; } /** * idle_cpu_without - would a given CPU be idle without p ? * @cpu: the processor on which idleness is tested. * @p: task which should be ignored. * * Return: 1 if the CPU would be idle. 0 otherwise. */ static int idle_cpu_without(int cpu, struct task_struct *p) { struct rq *rq = cpu_rq(cpu); if (rq->curr != rq->idle && rq->curr != p) return 0; /* * rq->nr_running can't be used but an updated version without the * impact of p on cpu must be used instead. The updated nr_running * be computed and tested before calling idle_cpu_without(). */ #ifdef CONFIG_SMP if (rq->ttwu_pending) return 0; #endif return 1; } /* * update_sg_wakeup_stats - Update sched_group's statistics for wakeup. * @sd: The sched_domain level to look for idlest group. * @group: sched_group whose statistics are to be updated. * @sgs: variable to hold the statistics for this group. * @p: The task for which we look for the idlest group/CPU. */ static inline void update_sg_wakeup_stats(struct sched_domain *sd, struct sched_group *group, struct sg_lb_stats *sgs, struct task_struct *p) { int i, nr_running; memset(sgs, 0, sizeof(*sgs)); /* Assume that task can't fit any CPU of the group */ if (sd->flags & SD_ASYM_CPUCAPACITY) sgs->group_misfit_task_load = 1; for_each_cpu(i, sched_group_span(group)) { struct rq *rq = cpu_rq(i); unsigned int local; sgs->group_load += cpu_load_without(rq, p); sgs->group_util += cpu_util_without(i, p); sgs->group_runnable += cpu_runnable_without(rq, p); local = task_running_on_cpu(i, p); sgs->sum_h_nr_running += rq->cfs.h_nr_running - local; nr_running = rq->nr_running - local; sgs->sum_nr_running += nr_running; /* * No need to call idle_cpu_without() if nr_running is not 0 */ if (!nr_running && idle_cpu_without(i, p)) sgs->idle_cpus++; /* Check if task fits in the CPU */ if (sd->flags & SD_ASYM_CPUCAPACITY && sgs->group_misfit_task_load && task_fits_cpu(p, i)) sgs->group_misfit_task_load = 0; } sgs->group_capacity = group->sgc->capacity; sgs->group_weight = group->group_weight; sgs->group_type = group_classify(sd->imbalance_pct, group, sgs); /* * Computing avg_load makes sense only when group is fully busy or * overloaded */ if (sgs->group_type == group_fully_busy || sgs->group_type == group_overloaded) sgs->avg_load = (sgs->group_load * SCHED_CAPACITY_SCALE) / sgs->group_capacity; } static bool update_pick_idlest(struct sched_group *idlest, struct sg_lb_stats *idlest_sgs, struct sched_group *group, struct sg_lb_stats *sgs) { if (sgs->group_type < idlest_sgs->group_type) return true; if (sgs->group_type > idlest_sgs->group_type) return false; /* * The candidate and the current idlest group are the same type of * group. Let check which one is the idlest according to the type. */ switch (sgs->group_type) { case group_overloaded: case group_fully_busy: /* Select the group with lowest avg_load. */ if (idlest_sgs->avg_load <= sgs->avg_load) return false; break; case group_imbalanced: case group_asym_packing: case group_smt_balance: /* Those types are not used in the slow wakeup path */ return false; case group_misfit_task: /* Select group with the highest max capacity */ if (idlest->sgc->max_capacity >= group->sgc->max_capacity) return false; break; case group_has_spare: /* Select group with most idle CPUs */ if (idlest_sgs->idle_cpus > sgs->idle_cpus) return false; /* Select group with lowest group_util */ if (idlest_sgs->idle_cpus == sgs->idle_cpus && idlest_sgs->group_util <= sgs->group_util) return false; break; } return true; } /* * find_idlest_group() finds and returns the least busy CPU group within the * domain. * * Assumes p is allowed on at least one CPU in sd. */ static struct sched_group * find_idlest_group(struct sched_domain *sd, struct task_struct *p, int this_cpu) { struct sched_group *idlest = NULL, *local = NULL, *group = sd->groups; struct sg_lb_stats local_sgs, tmp_sgs; struct sg_lb_stats *sgs; unsigned long imbalance; struct sg_lb_stats idlest_sgs = { .avg_load = UINT_MAX, .group_type = group_overloaded, }; do { int local_group; /* Skip over this group if it has no CPUs allowed */ if (!cpumask_intersects(sched_group_span(group), p->cpus_ptr)) continue; /* Skip over this group if no cookie matched */ if (!sched_group_cookie_match(cpu_rq(this_cpu), p, group)) continue; local_group = cpumask_test_cpu(this_cpu, sched_group_span(group)); if (local_group) { sgs = &local_sgs; local = group; } else { sgs = &tmp_sgs; } update_sg_wakeup_stats(sd, group, sgs, p); if (!local_group && update_pick_idlest(idlest, &idlest_sgs, group, sgs)) { idlest = group; idlest_sgs = *sgs; } } while (group = group->next, group != sd->groups); /* There is no idlest group to push tasks to */ if (!idlest) return NULL; /* The local group has been skipped because of CPU affinity */ if (!local) return idlest; /* * If the local group is idler than the selected idlest group * don't try and push the task. */ if (local_sgs.group_type < idlest_sgs.group_type) return NULL; /* * If the local group is busier than the selected idlest group * try and push the task. */ if (local_sgs.group_type > idlest_sgs.group_type) return idlest; switch (local_sgs.group_type) { case group_overloaded: case group_fully_busy: /* Calculate allowed imbalance based on load */ imbalance = scale_load_down(NICE_0_LOAD) * (sd->imbalance_pct-100) / 100; /* * When comparing groups across NUMA domains, it's possible for * the local domain to be very lightly loaded relative to the * remote domains but "imbalance" skews the comparison making * remote CPUs look much more favourable. When considering * cross-domain, add imbalance to the load on the remote node * and consider staying local. */ if ((sd->flags & SD_NUMA) && ((idlest_sgs.avg_load + imbalance) >= local_sgs.avg_load)) return NULL; /* * If the local group is less loaded than the selected * idlest group don't try and push any tasks. */ if (idlest_sgs.avg_load >= (local_sgs.avg_load + imbalance)) return NULL; if (100 * local_sgs.avg_load <= sd->imbalance_pct * idlest_sgs.avg_load) return NULL; break; case group_imbalanced: case group_asym_packing: case group_smt_balance: /* Those type are not used in the slow wakeup path */ return NULL; case group_misfit_task: /* Select group with the highest max capacity */ if (local->sgc->max_capacity >= idlest->sgc->max_capacity) return NULL; break; case group_has_spare: #ifdef CONFIG_NUMA if (sd->flags & SD_NUMA) { int imb_numa_nr = sd->imb_numa_nr; #ifdef CONFIG_NUMA_BALANCING int idlest_cpu; /* * If there is spare capacity at NUMA, try to select * the preferred node */ if (cpu_to_node(this_cpu) == p->numa_preferred_nid) return NULL; idlest_cpu = cpumask_first(sched_group_span(idlest)); if (cpu_to_node(idlest_cpu) == p->numa_preferred_nid) return idlest; #endif /* CONFIG_NUMA_BALANCING */ /* * Otherwise, keep the task close to the wakeup source * and improve locality if the number of running tasks * would remain below threshold where an imbalance is * allowed while accounting for the possibility the * task is pinned to a subset of CPUs. If there is a * real need of migration, periodic load balance will * take care of it. */ if (p->nr_cpus_allowed != NR_CPUS) { struct cpumask *cpus = this_cpu_cpumask_var_ptr(select_rq_mask); cpumask_and(cpus, sched_group_span(local), p->cpus_ptr); imb_numa_nr = min(cpumask_weight(cpus), sd->imb_numa_nr); } imbalance = abs(local_sgs.idle_cpus - idlest_sgs.idle_cpus); if (!adjust_numa_imbalance(imbalance, local_sgs.sum_nr_running + 1, imb_numa_nr)) { return NULL; } } #endif /* CONFIG_NUMA */ /* * Select group with highest number of idle CPUs. We could also * compare the utilization which is more stable but it can end * up that the group has less spare capacity but finally more * idle CPUs which means more opportunity to run task. */ if (local_sgs.idle_cpus >= idlest_sgs.idle_cpus) return NULL; break; } return idlest; } static void update_idle_cpu_scan(struct lb_env *env, unsigned long sum_util) { struct sched_domain_shared *sd_share; int llc_weight, pct; u64 x, y, tmp; /* * Update the number of CPUs to scan in LLC domain, which could * be used as a hint in select_idle_cpu(). The update of sd_share * could be expensive because it is within a shared cache line. * So the write of this hint only occurs during periodic load * balancing, rather than CPU_NEWLY_IDLE, because the latter * can fire way more frequently than the former. */ if (!sched_feat(SIS_UTIL) || env->idle == CPU_NEWLY_IDLE) return; llc_weight = per_cpu(sd_llc_size, env->dst_cpu); if (env->sd->span_weight != llc_weight) return; sd_share = rcu_dereference(per_cpu(sd_llc_shared, env->dst_cpu)); if (!sd_share) return; /* * The number of CPUs to search drops as sum_util increases, when * sum_util hits 85% or above, the scan stops. * The reason to choose 85% as the threshold is because this is the * imbalance_pct(117) when a LLC sched group is overloaded. * * let y = SCHED_CAPACITY_SCALE - p * x^2 [1] * and y'= y / SCHED_CAPACITY_SCALE * * x is the ratio of sum_util compared to the CPU capacity: * x = sum_util / (llc_weight * SCHED_CAPACITY_SCALE) * y' is the ratio of CPUs to be scanned in the LLC domain, * and the number of CPUs to scan is calculated by: * * nr_scan = llc_weight * y' [2] * * When x hits the threshold of overloaded, AKA, when * x = 100 / pct, y drops to 0. According to [1], * p should be SCHED_CAPACITY_SCALE * pct^2 / 10000 * * Scale x by SCHED_CAPACITY_SCALE: * x' = sum_util / llc_weight; [3] * * and finally [1] becomes: * y = SCHED_CAPACITY_SCALE - * x'^2 * pct^2 / (10000 * SCHED_CAPACITY_SCALE) [4] * */ /* equation [3] */ x = sum_util; do_div(x, llc_weight); /* equation [4] */ pct = env->sd->imbalance_pct; tmp = x * x * pct * pct; do_div(tmp, 10000 * SCHED_CAPACITY_SCALE); tmp = min_t(long, tmp, SCHED_CAPACITY_SCALE); y = SCHED_CAPACITY_SCALE - tmp; /* equation [2] */ y *= llc_weight; do_div(y, SCHED_CAPACITY_SCALE); if ((int)y != sd_share->nr_idle_scan) WRITE_ONCE(sd_share->nr_idle_scan, (int)y); } /** * update_sd_lb_stats - Update sched_domain's statistics for load balancing. * @env: The load balancing environment. * @sds: variable to hold the statistics for this sched_domain. */ static inline void update_sd_lb_stats(struct lb_env *env, struct sd_lb_stats *sds) { struct sched_group *sg = env->sd->groups; struct sg_lb_stats *local = &sds->local_stat; struct sg_lb_stats tmp_sgs; unsigned long sum_util = 0; int sg_status = 0; do { struct sg_lb_stats *sgs = &tmp_sgs; int local_group; local_group = cpumask_test_cpu(env->dst_cpu, sched_group_span(sg)); if (local_group) { sds->local = sg; sgs = local; if (env->idle != CPU_NEWLY_IDLE || time_after_eq(jiffies, sg->sgc->next_update)) update_group_capacity(env->sd, env->dst_cpu); } update_sg_lb_stats(env, sds, sg, sgs, &sg_status); if (local_group) goto next_group; if (update_sd_pick_busiest(env, sds, sg, sgs)) { sds->busiest = sg; sds->busiest_stat = *sgs; } next_group: /* Now, start updating sd_lb_stats */ sds->total_load += sgs->group_load; sds->total_capacity += sgs->group_capacity; sum_util += sgs->group_util; sg = sg->next; } while (sg != env->sd->groups); /* * Indicate that the child domain of the busiest group prefers tasks * go to a child's sibling domains first. NB the flags of a sched group * are those of the child domain. */ if (sds->busiest) sds->prefer_sibling = !!(sds->busiest->flags & SD_PREFER_SIBLING); if (env->sd->flags & SD_NUMA) env->fbq_type = fbq_classify_group(&sds->busiest_stat); if (!env->sd->parent) { struct root_domain *rd = env->dst_rq->rd; /* update overload indicator if we are at root domain */ WRITE_ONCE(rd->overload, sg_status & SG_OVERLOAD); /* Update over-utilization (tipping point, U >= 0) indicator */ WRITE_ONCE(rd->overutilized, sg_status & SG_OVERUTILIZED); trace_sched_overutilized_tp(rd, sg_status & SG_OVERUTILIZED); } else if (sg_status & SG_OVERUTILIZED) { struct root_domain *rd = env->dst_rq->rd; WRITE_ONCE(rd->overutilized, SG_OVERUTILIZED); trace_sched_overutilized_tp(rd, SG_OVERUTILIZED); } update_idle_cpu_scan(env, sum_util); } /** * calculate_imbalance - Calculate the amount of imbalance present within the * groups of a given sched_domain during load balance. * @env: load balance environment * @sds: statistics of the sched_domain whose imbalance is to be calculated. */ static inline void calculate_imbalance(struct lb_env *env, struct sd_lb_stats *sds) { struct sg_lb_stats *local, *busiest; local = &sds->local_stat; busiest = &sds->busiest_stat; if (busiest->group_type == group_misfit_task) { if (env->sd->flags & SD_ASYM_CPUCAPACITY) { /* Set imbalance to allow misfit tasks to be balanced. */ env->migration_type = migrate_misfit; env->imbalance = 1; } else { /* * Set load imbalance to allow moving task from cpu * with reduced capacity. */ env->migration_type = migrate_load; env->imbalance = busiest->group_misfit_task_load; } return; } if (busiest->group_type == group_asym_packing) { /* * In case of asym capacity, we will try to migrate all load to * the preferred CPU. */ env->migration_type = migrate_task; env->imbalance = busiest->sum_h_nr_running; return; } if (busiest->group_type == group_smt_balance) { /* Reduce number of tasks sharing CPU capacity */ env->migration_type = migrate_task; env->imbalance = 1; return; } if (busiest->group_type == group_imbalanced) { /* * In the group_imb case we cannot rely on group-wide averages * to ensure CPU-load equilibrium, try to move any task to fix * the imbalance. The next load balance will take care of * balancing back the system. */ env->migration_type = migrate_task; env->imbalance = 1; return; } /* * Try to use spare capacity of local group without overloading it or * emptying busiest. */ if (local->group_type == group_has_spare) { if ((busiest->group_type > group_fully_busy) && !(env->sd->flags & SD_SHARE_PKG_RESOURCES)) { /* * If busiest is overloaded, try to fill spare * capacity. This might end up creating spare capacity * in busiest or busiest still being overloaded but * there is no simple way to directly compute the * amount of load to migrate in order to balance the * system. */ env->migration_type = migrate_util; env->imbalance = max(local->group_capacity, local->group_util) - local->group_util; /* * In some cases, the group's utilization is max or even * higher than capacity because of migrations but the * local CPU is (newly) idle. There is at least one * waiting task in this overloaded busiest group. Let's * try to pull it. */ if (env->idle != CPU_NOT_IDLE && env->imbalance == 0) { env->migration_type = migrate_task; env->imbalance = 1; } return; } if (busiest->group_weight == 1 || sds->prefer_sibling) { /* * When prefer sibling, evenly spread running tasks on * groups. */ env->migration_type = migrate_task; env->imbalance = sibling_imbalance(env, sds, busiest, local); } else { /* * If there is no overload, we just want to even the number of * idle cpus. */ env->migration_type = migrate_task; env->imbalance = max_t(long, 0, (local->idle_cpus - busiest->idle_cpus)); } #ifdef CONFIG_NUMA /* Consider allowing a small imbalance between NUMA groups */ if (env->sd->flags & SD_NUMA) { env->imbalance = adjust_numa_imbalance(env->imbalance, local->sum_nr_running + 1, env->sd->imb_numa_nr); } #endif /* Number of tasks to move to restore balance */ env->imbalance >>= 1; return; } /* * Local is fully busy but has to take more load to relieve the * busiest group */ if (local->group_type < group_overloaded) { /* * Local will become overloaded so the avg_load metrics are * finally needed. */ local->avg_load = (local->group_load * SCHED_CAPACITY_SCALE) / local->group_capacity; /* * If the local group is more loaded than the selected * busiest group don't try to pull any tasks. */ if (local->avg_load >= busiest->avg_load) { env->imbalance = 0; return; } sds->avg_load = (sds->total_load * SCHED_CAPACITY_SCALE) / sds->total_capacity; /* * If the local group is more loaded than the average system * load, don't try to pull any tasks. */ if (local->avg_load >= sds->avg_load) { env->imbalance = 0; return; } } /* * Both group are or will become overloaded and we're trying to get all * the CPUs to the average_load, so we don't want to push ourselves * above the average load, nor do we wish to reduce the max loaded CPU * below the average load. At the same time, we also don't want to * reduce the group load below the group capacity. Thus we look for * the minimum possible imbalance. */ env->migration_type = migrate_load; env->imbalance = min( (busiest->avg_load - sds->avg_load) * busiest->group_capacity, (sds->avg_load - local->avg_load) * local->group_capacity ) / SCHED_CAPACITY_SCALE; } /******* find_busiest_group() helpers end here *********************/ /* * Decision matrix according to the local and busiest group type: * * busiest \ local has_spare fully_busy misfit asym imbalanced overloaded * has_spare nr_idle balanced N/A N/A balanced balanced * fully_busy nr_idle nr_idle N/A N/A balanced balanced * misfit_task force N/A N/A N/A N/A N/A * asym_packing force force N/A N/A force force * imbalanced force force N/A N/A force force * overloaded force force N/A N/A force avg_load * * N/A : Not Applicable because already filtered while updating * statistics. * balanced : The system is balanced for these 2 groups. * force : Calculate the imbalance as load migration is probably needed. * avg_load : Only if imbalance is significant enough. * nr_idle : dst_cpu is not busy and the number of idle CPUs is quite * different in groups. */ /** * find_busiest_group - Returns the busiest group within the sched_domain * if there is an imbalance. * @env: The load balancing environment. * * Also calculates the amount of runnable load which should be moved * to restore balance. * * Return: - The busiest group if imbalance exists. */ static struct sched_group *find_busiest_group(struct lb_env *env) { struct sg_lb_stats *local, *busiest; struct sd_lb_stats sds; init_sd_lb_stats(&sds); /* * Compute the various statistics relevant for load balancing at * this level. */ update_sd_lb_stats(env, &sds); /* There is no busy sibling group to pull tasks from */ if (!sds.busiest) goto out_balanced; busiest = &sds.busiest_stat; /* Misfit tasks should be dealt with regardless of the avg load */ if (busiest->group_type == group_misfit_task) goto force_balance; if (sched_energy_enabled()) { struct root_domain *rd = env->dst_rq->rd; if (rcu_dereference(rd->pd) && !READ_ONCE(rd->overutilized)) goto out_balanced; } /* ASYM feature bypasses nice load balance check */ if (busiest->group_type == group_asym_packing) goto force_balance; /* * If the busiest group is imbalanced the below checks don't * work because they assume all things are equal, which typically * isn't true due to cpus_ptr constraints and the like. */ if (busiest->group_type == group_imbalanced) goto force_balance; local = &sds.local_stat; /* * If the local group is busier than the selected busiest group * don't try and pull any tasks. */ if (local->group_type > busiest->group_type) goto out_balanced; /* * When groups are overloaded, use the avg_load to ensure fairness * between tasks. */ if (local->group_type == group_overloaded) { /* * If the local group is more loaded than the selected * busiest group don't try to pull any tasks. */ if (local->avg_load >= busiest->avg_load) goto out_balanced; /* XXX broken for overlapping NUMA groups */ sds.avg_load = (sds.total_load * SCHED_CAPACITY_SCALE) / sds.total_capacity; /* * Don't pull any tasks if this group is already above the * domain average load. */ if (local->avg_load >= sds.avg_load) goto out_balanced; /* * If the busiest group is more loaded, use imbalance_pct to be * conservative. */ if (100 * busiest->avg_load <= env->sd->imbalance_pct * local->avg_load) goto out_balanced; } /* * Try to move all excess tasks to a sibling domain of the busiest * group's child domain. */ if (sds.prefer_sibling && local->group_type == group_has_spare && sibling_imbalance(env, &sds, busiest, local) > 1) goto force_balance; if (busiest->group_type != group_overloaded) { if (env->idle == CPU_NOT_IDLE) { /* * If the busiest group is not overloaded (and as a * result the local one too) but this CPU is already * busy, let another idle CPU try to pull task. */ goto out_balanced; } if (busiest->group_type == group_smt_balance && smt_vs_nonsmt_groups(sds.local, sds.busiest)) { /* Let non SMT CPU pull from SMT CPU sharing with sibling */ goto force_balance; } if (busiest->group_weight > 1 && local->idle_cpus <= (busiest->idle_cpus + 1)) { /* * If the busiest group is not overloaded * and there is no imbalance between this and busiest * group wrt idle CPUs, it is balanced. The imbalance * becomes significant if the diff is greater than 1 * otherwise we might end up to just move the imbalance * on another group. Of course this applies only if * there is more than 1 CPU per group. */ goto out_balanced; } if (busiest->sum_h_nr_running == 1) { /* * busiest doesn't have any tasks waiting to run */ goto out_balanced; } } force_balance: /* Looks like there is an imbalance. Compute it */ calculate_imbalance(env, &sds); return env->imbalance ? sds.busiest : NULL; out_balanced: env->imbalance = 0; return NULL; } /* * find_busiest_queue - find the busiest runqueue among the CPUs in the group. */ static struct rq *find_busiest_queue(struct lb_env *env, struct sched_group *group) { struct rq *busiest = NULL, *rq; unsigned long busiest_util = 0, busiest_load = 0, busiest_capacity = 1; unsigned int busiest_nr = 0; int i; for_each_cpu_and(i, sched_group_span(group), env->cpus) { unsigned long capacity, load, util; unsigned int nr_running; enum fbq_type rt; rq = cpu_rq(i); rt = fbq_classify_rq(rq); /* * We classify groups/runqueues into three groups: * - regular: there are !numa tasks * - remote: there are numa tasks that run on the 'wrong' node * - all: there is no distinction * * In order to avoid migrating ideally placed numa tasks, * ignore those when there's better options. * * If we ignore the actual busiest queue to migrate another * task, the next balance pass can still reduce the busiest * queue by moving tasks around inside the node. * * If we cannot move enough load due to this classification * the next pass will adjust the group classification and * allow migration of more tasks. * * Both cases only affect the total convergence complexity. */ if (rt > env->fbq_type) continue; nr_running = rq->cfs.h_nr_running; if (!nr_running) continue; capacity = capacity_of(i); /* * For ASYM_CPUCAPACITY domains, don't pick a CPU that could * eventually lead to active_balancing high->low capacity. * Higher per-CPU capacity is considered better than balancing * average load. */ if (env->sd->flags & SD_ASYM_CPUCAPACITY && !capacity_greater(capacity_of(env->dst_cpu), capacity) && nr_running == 1) continue; /* * Make sure we only pull tasks from a CPU of lower priority * when balancing between SMT siblings. * * If balancing between cores, let lower priority CPUs help * SMT cores with more than one busy sibling. */ if ((env->sd->flags & SD_ASYM_PACKING) && sched_use_asym_prio(env->sd, i) && sched_asym_prefer(i, env->dst_cpu) && nr_running == 1) continue; switch (env->migration_type) { case migrate_load: /* * When comparing with load imbalance, use cpu_load() * which is not scaled with the CPU capacity. */ load = cpu_load(rq); if (nr_running == 1 && load > env->imbalance && !check_cpu_capacity(rq, env->sd)) break; /* * For the load comparisons with the other CPUs, * consider the cpu_load() scaled with the CPU * capacity, so that the load can be moved away * from the CPU that is potentially running at a * lower capacity. * * Thus we're looking for max(load_i / capacity_i), * crosswise multiplication to rid ourselves of the * division works out to: * load_i * capacity_j > load_j * capacity_i; * where j is our previous maximum. */ if (load * busiest_capacity > busiest_load * capacity) { busiest_load = load; busiest_capacity = capacity; busiest = rq; } break; case migrate_util: util = cpu_util_cfs_boost(i); /* * Don't try to pull utilization from a CPU with one * running task. Whatever its utilization, we will fail * detach the task. */ if (nr_running <= 1) continue; if (busiest_util < util) { busiest_util = util; busiest = rq; } break; case migrate_task: if (busiest_nr < nr_running) { busiest_nr = nr_running; busiest = rq; } break; case migrate_misfit: /* * For ASYM_CPUCAPACITY domains with misfit tasks we * simply seek the "biggest" misfit task. */ if (rq->misfit_task_load > busiest_load) { busiest_load = rq->misfit_task_load; busiest = rq; } break; } } return busiest; } /* * Max backoff if we encounter pinned tasks. Pretty arbitrary value, but * so long as it is large enough. */ #define MAX_PINNED_INTERVAL 512 static inline bool asym_active_balance(struct lb_env *env) { /* * ASYM_PACKING needs to force migrate tasks from busy but lower * priority CPUs in order to pack all tasks in the highest priority * CPUs. When done between cores, do it only if the whole core if the * whole core is idle. * * If @env::src_cpu is an SMT core with busy siblings, let * the lower priority @env::dst_cpu help it. Do not follow * CPU priority. */ return env->idle != CPU_NOT_IDLE && (env->sd->flags & SD_ASYM_PACKING) && sched_use_asym_prio(env->sd, env->dst_cpu) && (sched_asym_prefer(env->dst_cpu, env->src_cpu) || !sched_use_asym_prio(env->sd, env->src_cpu)); } static inline bool imbalanced_active_balance(struct lb_env *env) { struct sched_domain *sd = env->sd; /* * The imbalanced case includes the case of pinned tasks preventing a fair * distribution of the load on the system but also the even distribution of the * threads on a system with spare capacity */ if ((env->migration_type == migrate_task) && (sd->nr_balance_failed > sd->cache_nice_tries+2)) return 1; return 0; } static int need_active_balance(struct lb_env *env) { struct sched_domain *sd = env->sd; if (asym_active_balance(env)) return 1; if (imbalanced_active_balance(env)) return 1; /* * The dst_cpu is idle and the src_cpu CPU has only 1 CFS task. * It's worth migrating the task if the src_cpu's capacity is reduced * because of other sched_class or IRQs if more capacity stays * available on dst_cpu. */ if ((env->idle != CPU_NOT_IDLE) && (env->src_rq->cfs.h_nr_running == 1)) { if ((check_cpu_capacity(env->src_rq, sd)) && (capacity_of(env->src_cpu)*sd->imbalance_pct < capacity_of(env->dst_cpu)*100)) return 1; } if (env->migration_type == migrate_misfit) return 1; return 0; } static int active_load_balance_cpu_stop(void *data); static int should_we_balance(struct lb_env *env) { struct cpumask *swb_cpus = this_cpu_cpumask_var_ptr(should_we_balance_tmpmask); struct sched_group *sg = env->sd->groups; int cpu, idle_smt = -1; /* * Ensure the balancing environment is consistent; can happen * when the softirq triggers 'during' hotplug. */ if (!cpumask_test_cpu(env->dst_cpu, env->cpus)) return 0; /* * In the newly idle case, we will allow all the CPUs * to do the newly idle load balance. * * However, we bail out if we already have tasks or a wakeup pending, * to optimize wakeup latency. */ if (env->idle == CPU_NEWLY_IDLE) { if (env->dst_rq->nr_running > 0 || env->dst_rq->ttwu_pending) return 0; return 1; } cpumask_copy(swb_cpus, group_balance_mask(sg)); /* Try to find first idle CPU */ for_each_cpu_and(cpu, swb_cpus, env->cpus) { if (!idle_cpu(cpu)) continue; /* * Don't balance to idle SMT in busy core right away when * balancing cores, but remember the first idle SMT CPU for * later consideration. Find CPU on an idle core first. */ if (!(env->sd->flags & SD_SHARE_CPUCAPACITY) && !is_core_idle(cpu)) { if (idle_smt == -1) idle_smt = cpu; /* * If the core is not idle, and first SMT sibling which is * idle has been found, then its not needed to check other * SMT siblings for idleness: */ #ifdef CONFIG_SCHED_SMT cpumask_andnot(swb_cpus, swb_cpus, cpu_smt_mask(cpu)); #endif continue; } /* * Are we the first idle core in a non-SMT domain or higher, * or the first idle CPU in a SMT domain? */ return cpu == env->dst_cpu; } /* Are we the first idle CPU with busy siblings? */ if (idle_smt != -1) return idle_smt == env->dst_cpu; /* Are we the first CPU of this group ? */ return group_balance_cpu(sg) == env->dst_cpu; } /* * Check this_cpu to ensure it is balanced within domain. Attempt to move * tasks if there is an imbalance. */ static int load_balance(int this_cpu, struct rq *this_rq, struct sched_domain *sd, enum cpu_idle_type idle, int *continue_balancing) { int ld_moved, cur_ld_moved, active_balance = 0; struct sched_domain *sd_parent = sd->parent; struct sched_group *group; struct rq *busiest; struct rq_flags rf; struct cpumask *cpus = this_cpu_cpumask_var_ptr(load_balance_mask); struct lb_env env = { .sd = sd, .dst_cpu = this_cpu, .dst_rq = this_rq, .dst_grpmask = group_balance_mask(sd->groups), .idle = idle, .loop_break = SCHED_NR_MIGRATE_BREAK, .cpus = cpus, .fbq_type = all, .tasks = LIST_HEAD_INIT(env.tasks), }; cpumask_and(cpus, sched_domain_span(sd), cpu_active_mask); schedstat_inc(sd->lb_count[idle]); redo: if (!should_we_balance(&env)) { *continue_balancing = 0; goto out_balanced; } group = find_busiest_group(&env); if (!group) { schedstat_inc(sd->lb_nobusyg[idle]); goto out_balanced; } busiest = find_busiest_queue(&env, group); if (!busiest) { schedstat_inc(sd->lb_nobusyq[idle]); goto out_balanced; } WARN_ON_ONCE(busiest == env.dst_rq); schedstat_add(sd->lb_imbalance[idle], env.imbalance); env.src_cpu = busiest->cpu; env.src_rq = busiest; ld_moved = 0; /* Clear this flag as soon as we find a pullable task */ env.flags |= LBF_ALL_PINNED; if (busiest->nr_running > 1) { /* * Attempt to move tasks. If find_busiest_group has found * an imbalance but busiest->nr_running <= 1, the group is * still unbalanced. ld_moved simply stays zero, so it is * correctly treated as an imbalance. */ env.loop_max = min(sysctl_sched_nr_migrate, busiest->nr_running); more_balance: rq_lock_irqsave(busiest, &rf); update_rq_clock(busiest); /* * cur_ld_moved - load moved in current iteration * ld_moved - cumulative load moved across iterations */ cur_ld_moved = detach_tasks(&env); /* * We've detached some tasks from busiest_rq. Every * task is masked "TASK_ON_RQ_MIGRATING", so we can safely * unlock busiest->lock, and we are able to be sure * that nobody can manipulate the tasks in parallel. * See task_rq_lock() family for the details. */ rq_unlock(busiest, &rf); if (cur_ld_moved) { attach_tasks(&env); ld_moved += cur_ld_moved; } local_irq_restore(rf.flags); if (env.flags & LBF_NEED_BREAK) { env.flags &= ~LBF_NEED_BREAK; /* Stop if we tried all running tasks */ if (env.loop < busiest->nr_running) goto more_balance; } /* * Revisit (affine) tasks on src_cpu that couldn't be moved to * us and move them to an alternate dst_cpu in our sched_group * where they can run. The upper limit on how many times we * iterate on same src_cpu is dependent on number of CPUs in our * sched_group. * * This changes load balance semantics a bit on who can move * load to a given_cpu. In addition to the given_cpu itself * (or a ilb_cpu acting on its behalf where given_cpu is * nohz-idle), we now have balance_cpu in a position to move * load to given_cpu. In rare situations, this may cause * conflicts (balance_cpu and given_cpu/ilb_cpu deciding * _independently_ and at _same_ time to move some load to * given_cpu) causing excess load to be moved to given_cpu. * This however should not happen so much in practice and * moreover subsequent load balance cycles should correct the * excess load moved. */ if ((env.flags & LBF_DST_PINNED) && env.imbalance > 0) { /* Prevent to re-select dst_cpu via env's CPUs */ __cpumask_clear_cpu(env.dst_cpu, env.cpus); env.dst_rq = cpu_rq(env.new_dst_cpu); env.dst_cpu = env.new_dst_cpu; env.flags &= ~LBF_DST_PINNED; env.loop = 0; env.loop_break = SCHED_NR_MIGRATE_BREAK; /* * Go back to "more_balance" rather than "redo" since we * need to continue with same src_cpu. */ goto more_balance; } /* * We failed to reach balance because of affinity. */ if (sd_parent) { int *group_imbalance = &sd_parent->groups->sgc->imbalance; if ((env.flags & LBF_SOME_PINNED) && env.imbalance > 0) *group_imbalance = 1; } /* All tasks on this runqueue were pinned by CPU affinity */ if (unlikely(env.flags & LBF_ALL_PINNED)) { __cpumask_clear_cpu(cpu_of(busiest), cpus); /* * Attempting to continue load balancing at the current * sched_domain level only makes sense if there are * active CPUs remaining as possible busiest CPUs to * pull load from which are not contained within the * destination group that is receiving any migrated * load. */ if (!cpumask_subset(cpus, env.dst_grpmask)) { env.loop = 0; env.loop_break = SCHED_NR_MIGRATE_BREAK; goto redo; } goto out_all_pinned; } } if (!ld_moved) { schedstat_inc(sd->lb_failed[idle]); /* * Increment the failure counter only on periodic balance. * We do not want newidle balance, which can be very * frequent, pollute the failure counter causing * excessive cache_hot migrations and active balances. */ if (idle != CPU_NEWLY_IDLE) sd->nr_balance_failed++; if (need_active_balance(&env)) { unsigned long flags; raw_spin_rq_lock_irqsave(busiest, flags); /* * Don't kick the active_load_balance_cpu_stop, * if the curr task on busiest CPU can't be * moved to this_cpu: */ if (!cpumask_test_cpu(this_cpu, busiest->curr->cpus_ptr)) { raw_spin_rq_unlock_irqrestore(busiest, flags); goto out_one_pinned; } /* Record that we found at least one task that could run on this_cpu */ env.flags &= ~LBF_ALL_PINNED; /* * ->active_balance synchronizes accesses to * ->active_balance_work. Once set, it's cleared * only after active load balance is finished. */ if (!busiest->active_balance) { busiest->active_balance = 1; busiest->push_cpu = this_cpu; active_balance = 1; } preempt_disable(); raw_spin_rq_unlock_irqrestore(busiest, flags); if (active_balance) { stop_one_cpu_nowait(cpu_of(busiest), active_load_balance_cpu_stop, busiest, &busiest->active_balance_work); } preempt_enable(); } } else { sd->nr_balance_failed = 0; } if (likely(!active_balance) || need_active_balance(&env)) { /* We were unbalanced, so reset the balancing interval */ sd->balance_interval = sd->min_interval; } goto out; out_balanced: /* * We reach balance although we may have faced some affinity * constraints. Clear the imbalance flag only if other tasks got * a chance to move and fix the imbalance. */ if (sd_parent && !(env.flags & LBF_ALL_PINNED)) { int *group_imbalance = &sd_parent->groups->sgc->imbalance; if (*group_imbalance) *group_imbalance = 0; } out_all_pinned: /* * We reach balance because all tasks are pinned at this level so * we can't migrate them. Let the imbalance flag set so parent level * can try to migrate them. */ schedstat_inc(sd->lb_balanced[idle]); sd->nr_balance_failed = 0; out_one_pinned: ld_moved = 0; /* * newidle_balance() disregards balance intervals, so we could * repeatedly reach this code, which would lead to balance_interval * skyrocketing in a short amount of time. Skip the balance_interval * increase logic to avoid that. */ if (env.idle == CPU_NEWLY_IDLE) goto out; /* tune up the balancing interval */ if ((env.flags & LBF_ALL_PINNED && sd->balance_interval < MAX_PINNED_INTERVAL) || sd->balance_interval < sd->max_interval) sd->balance_interval *= 2; out: return ld_moved; } static inline unsigned long get_sd_balance_interval(struct sched_domain *sd, int cpu_busy) { unsigned long interval = sd->balance_interval; if (cpu_busy) interval *= sd->busy_factor; /* scale ms to jiffies */ interval = msecs_to_jiffies(interval); /* * Reduce likelihood of busy balancing at higher domains racing with * balancing at lower domains by preventing their balancing periods * from being multiples of each other. */ if (cpu_busy) interval -= 1; interval = clamp(interval, 1UL, max_load_balance_interval); return interval; } static inline void update_next_balance(struct sched_domain *sd, unsigned long *next_balance) { unsigned long interval, next; /* used by idle balance, so cpu_busy = 0 */ interval = get_sd_balance_interval(sd, 0); next = sd->last_balance + interval; if (time_after(*next_balance, next)) *next_balance = next; } /* * active_load_balance_cpu_stop is run by the CPU stopper. It pushes * running tasks off the busiest CPU onto idle CPUs. It requires at * least 1 task to be running on each physical CPU where possible, and * avoids physical / logical imbalances. */ static int active_load_balance_cpu_stop(void *data) { struct rq *busiest_rq = data; int busiest_cpu = cpu_of(busiest_rq); int target_cpu = busiest_rq->push_cpu; struct rq *target_rq = cpu_rq(target_cpu); struct sched_domain *sd; struct task_struct *p = NULL; struct rq_flags rf; rq_lock_irq(busiest_rq, &rf); /* * Between queueing the stop-work and running it is a hole in which * CPUs can become inactive. We should not move tasks from or to * inactive CPUs. */ if (!cpu_active(busiest_cpu) || !cpu_active(target_cpu)) goto out_unlock; /* Make sure the requested CPU hasn't gone down in the meantime: */ if (unlikely(busiest_cpu != smp_processor_id() || !busiest_rq->active_balance)) goto out_unlock; /* Is there any task to move? */ if (busiest_rq->nr_running <= 1) goto out_unlock; /* * This condition is "impossible", if it occurs * we need to fix it. Originally reported by * Bjorn Helgaas on a 128-CPU setup. */ WARN_ON_ONCE(busiest_rq == target_rq); /* Search for an sd spanning us and the target CPU. */ rcu_read_lock(); for_each_domain(target_cpu, sd) { if (cpumask_test_cpu(busiest_cpu, sched_domain_span(sd))) break; } if (likely(sd)) { struct lb_env env = { .sd = sd, .dst_cpu = target_cpu, .dst_rq = target_rq, .src_cpu = busiest_rq->cpu, .src_rq = busiest_rq, .idle = CPU_IDLE, .flags = LBF_ACTIVE_LB, }; schedstat_inc(sd->alb_count); update_rq_clock(busiest_rq); p = detach_one_task(&env); if (p) { schedstat_inc(sd->alb_pushed); /* Active balancing done, reset the failure counter. */ sd->nr_balance_failed = 0; } else { schedstat_inc(sd->alb_failed); } } rcu_read_unlock(); out_unlock: busiest_rq->active_balance = 0; rq_unlock(busiest_rq, &rf); if (p) attach_one_task(target_rq, p); local_irq_enable(); return 0; } static DEFINE_SPINLOCK(balancing); /* * Scale the max load_balance interval with the number of CPUs in the system. * This trades load-balance latency on larger machines for less cross talk. */ void update_max_interval(void) { max_load_balance_interval = HZ*num_online_cpus()/10; } static inline bool update_newidle_cost(struct sched_domain *sd, u64 cost) { if (cost > sd->max_newidle_lb_cost) { /* * Track max cost of a domain to make sure to not delay the * next wakeup on the CPU. */ sd->max_newidle_lb_cost = cost; sd->last_decay_max_lb_cost = jiffies; } else if (time_after(jiffies, sd->last_decay_max_lb_cost + HZ)) { /* * Decay the newidle max times by ~1% per second to ensure that * it is not outdated and the current max cost is actually * shorter. */ sd->max_newidle_lb_cost = (sd->max_newidle_lb_cost * 253) / 256; sd->last_decay_max_lb_cost = jiffies; return true; } return false; } /* * It checks each scheduling domain to see if it is due to be balanced, * and initiates a balancing operation if so. * * Balancing parameters are set up in init_sched_domains. */ static void rebalance_domains(struct rq *rq, enum cpu_idle_type idle) { int continue_balancing = 1; int cpu = rq->cpu; int busy = idle != CPU_IDLE && !sched_idle_cpu(cpu); unsigned long interval; struct sched_domain *sd; /* Earliest time when we have to do rebalance again */ unsigned long next_balance = jiffies + 60*HZ; int update_next_balance = 0; int need_serialize, need_decay = 0; u64 max_cost = 0; rcu_read_lock(); for_each_domain(cpu, sd) { /* * Decay the newidle max times here because this is a regular * visit to all the domains. */ need_decay = update_newidle_cost(sd, 0); max_cost += sd->max_newidle_lb_cost; /* * Stop the load balance at this level. There is another * CPU in our sched group which is doing load balancing more * actively. */ if (!continue_balancing) { if (need_decay) continue; break; } interval = get_sd_balance_interval(sd, busy); need_serialize = sd->flags & SD_SERIALIZE; if (need_serialize) { if (!spin_trylock(&balancing)) goto out; } if (time_after_eq(jiffies, sd->last_balance + interval)) { if (load_balance(cpu, rq, sd, idle, &continue_balancing)) { /* * The LBF_DST_PINNED logic could have changed * env->dst_cpu, so we can't know our idle * state even if we migrated tasks. Update it. */ idle = idle_cpu(cpu) ? CPU_IDLE : CPU_NOT_IDLE; busy = idle != CPU_IDLE && !sched_idle_cpu(cpu); } sd->last_balance = jiffies; interval = get_sd_balance_interval(sd, busy); } if (need_serialize) spin_unlock(&balancing); out: if (time_after(next_balance, sd->last_balance + interval)) { next_balance = sd->last_balance + interval; update_next_balance = 1; } } if (need_decay) { /* * Ensure the rq-wide value also decays but keep it at a * reasonable floor to avoid funnies with rq->avg_idle. */ rq->max_idle_balance_cost = max((u64)sysctl_sched_migration_cost, max_cost); } rcu_read_unlock(); /* * next_balance will be updated only when there is a need. * When the cpu is attached to null domain for ex, it will not be * updated. */ if (likely(update_next_balance)) rq->next_balance = next_balance; } static inline int on_null_domain(struct rq *rq) { return unlikely(!rcu_dereference_sched(rq->sd)); } #ifdef CONFIG_NO_HZ_COMMON /* * NOHZ idle load balancing (ILB) details: * * - When one of the busy CPUs notices that there may be an idle rebalancing * needed, they will kick the idle load balancer, which then does idle * load balancing for all the idle CPUs. * * - HK_TYPE_MISC CPUs are used for this task, because HK_TYPE_SCHED is not set * anywhere yet. */ static inline int find_new_ilb(void) { const struct cpumask *hk_mask; int ilb_cpu; hk_mask = housekeeping_cpumask(HK_TYPE_MISC); for_each_cpu_and(ilb_cpu, nohz.idle_cpus_mask, hk_mask) { if (ilb_cpu == smp_processor_id()) continue; if (idle_cpu(ilb_cpu)) return ilb_cpu; } return -1; } /* * Kick a CPU to do the NOHZ balancing, if it is time for it, via a cross-CPU * SMP function call (IPI). * * We pick the first idle CPU in the HK_TYPE_MISC housekeeping set (if there is one). */ static void kick_ilb(unsigned int flags) { int ilb_cpu; /* * Increase nohz.next_balance only when if full ilb is triggered but * not if we only update stats. */ if (flags & NOHZ_BALANCE_KICK) nohz.next_balance = jiffies+1; ilb_cpu = find_new_ilb(); if (ilb_cpu < 0) return; /* * Access to rq::nohz_csd is serialized by NOHZ_KICK_MASK; he who sets * the first flag owns it; cleared by nohz_csd_func(). */ flags = atomic_fetch_or(flags, nohz_flags(ilb_cpu)); if (flags & NOHZ_KICK_MASK) return; /* * This way we generate an IPI on the target CPU which * is idle, and the softirq performing NOHZ idle load balancing * will be run before returning from the IPI. */ smp_call_function_single_async(ilb_cpu, &cpu_rq(ilb_cpu)->nohz_csd); } /* * Current decision point for kicking the idle load balancer in the presence * of idle CPUs in the system. */ static void nohz_balancer_kick(struct rq *rq) { unsigned long now = jiffies; struct sched_domain_shared *sds; struct sched_domain *sd; int nr_busy, i, cpu = rq->cpu; unsigned int flags = 0; if (unlikely(rq->idle_balance)) return; /* * We may be recently in ticked or tickless idle mode. At the first * busy tick after returning from idle, we will update the busy stats. */ nohz_balance_exit_idle(rq); /* * None are in tickless mode and hence no need for NOHZ idle load * balancing: */ if (likely(!atomic_read(&nohz.nr_cpus))) return; if (READ_ONCE(nohz.has_blocked) && time_after(now, READ_ONCE(nohz.next_blocked))) flags = NOHZ_STATS_KICK; if (time_before(now, nohz.next_balance)) goto out; if (rq->nr_running >= 2) { flags = NOHZ_STATS_KICK | NOHZ_BALANCE_KICK; goto out; } rcu_read_lock(); sd = rcu_dereference(rq->sd); if (sd) { /* * If there's a runnable CFS task and the current CPU has reduced * capacity, kick the ILB to see if there's a better CPU to run on: */ if (rq->cfs.h_nr_running >= 1 && check_cpu_capacity(rq, sd)) { flags = NOHZ_STATS_KICK | NOHZ_BALANCE_KICK; goto unlock; } } sd = rcu_dereference(per_cpu(sd_asym_packing, cpu)); if (sd) { /* * When ASYM_PACKING; see if there's a more preferred CPU * currently idle; in which case, kick the ILB to move tasks * around. * * When balancing betwen cores, all the SMT siblings of the * preferred CPU must be idle. */ for_each_cpu_and(i, sched_domain_span(sd), nohz.idle_cpus_mask) { if (sched_use_asym_prio(sd, i) && sched_asym_prefer(i, cpu)) { flags = NOHZ_STATS_KICK | NOHZ_BALANCE_KICK; goto unlock; } } } sd = rcu_dereference(per_cpu(sd_asym_cpucapacity, cpu)); if (sd) { /* * When ASYM_CPUCAPACITY; see if there's a higher capacity CPU * to run the misfit task on. */ if (check_misfit_status(rq, sd)) { flags = NOHZ_STATS_KICK | NOHZ_BALANCE_KICK; goto unlock; } /* * For asymmetric systems, we do not want to nicely balance * cache use, instead we want to embrace asymmetry and only * ensure tasks have enough CPU capacity. * * Skip the LLC logic because it's not relevant in that case. */ goto unlock; } sds = rcu_dereference(per_cpu(sd_llc_shared, cpu)); if (sds) { /* * If there is an imbalance between LLC domains (IOW we could * increase the overall cache utilization), we need a less-loaded LLC * domain to pull some load from. Likewise, we may need to spread * load within the current LLC domain (e.g. packed SMT cores but * other CPUs are idle). We can't really know from here how busy * the others are - so just get a NOHZ balance going if it looks * like this LLC domain has tasks we could move. */ nr_busy = atomic_read(&sds->nr_busy_cpus); if (nr_busy > 1) { flags = NOHZ_STATS_KICK | NOHZ_BALANCE_KICK; goto unlock; } } unlock: rcu_read_unlock(); out: if (READ_ONCE(nohz.needs_update)) flags |= NOHZ_NEXT_KICK; if (flags) kick_ilb(flags); } static void set_cpu_sd_state_busy(int cpu) { struct sched_domain *sd; rcu_read_lock(); sd = rcu_dereference(per_cpu(sd_llc, cpu)); if (!sd || !sd->nohz_idle) goto unlock; sd->nohz_idle = 0; atomic_inc(&sd->shared->nr_busy_cpus); unlock: rcu_read_unlock(); } void nohz_balance_exit_idle(struct rq *rq) { SCHED_WARN_ON(rq != this_rq()); if (likely(!rq->nohz_tick_stopped)) return; rq->nohz_tick_stopped = 0; cpumask_clear_cpu(rq->cpu, nohz.idle_cpus_mask); atomic_dec(&nohz.nr_cpus); set_cpu_sd_state_busy(rq->cpu); } static void set_cpu_sd_state_idle(int cpu) { struct sched_domain *sd; rcu_read_lock(); sd = rcu_dereference(per_cpu(sd_llc, cpu)); if (!sd || sd->nohz_idle) goto unlock; sd->nohz_idle = 1; atomic_dec(&sd->shared->nr_busy_cpus); unlock: rcu_read_unlock(); } /* * This routine will record that the CPU is going idle with tick stopped. * This info will be used in performing idle load balancing in the future. */ void nohz_balance_enter_idle(int cpu) { struct rq *rq = cpu_rq(cpu); SCHED_WARN_ON(cpu != smp_processor_id()); /* If this CPU is going down, then nothing needs to be done: */ if (!cpu_active(cpu)) return; /* Spare idle load balancing on CPUs that don't want to be disturbed: */ if (!housekeeping_cpu(cpu, HK_TYPE_SCHED)) return; /* * Can be set safely without rq->lock held * If a clear happens, it will have evaluated last additions because * rq->lock is held during the check and the clear */ rq->has_blocked_load = 1; /* * The tick is still stopped but load could have been added in the * meantime. We set the nohz.has_blocked flag to trig a check of the * *_avg. The CPU is already part of nohz.idle_cpus_mask so the clear * of nohz.has_blocked can only happen after checking the new load */ if (rq->nohz_tick_stopped) goto out; /* If we're a completely isolated CPU, we don't play: */ if (on_null_domain(rq)) return; rq->nohz_tick_stopped = 1; cpumask_set_cpu(cpu, nohz.idle_cpus_mask); atomic_inc(&nohz.nr_cpus); /* * Ensures that if nohz_idle_balance() fails to observe our * @idle_cpus_mask store, it must observe the @has_blocked * and @needs_update stores. */ smp_mb__after_atomic(); set_cpu_sd_state_idle(cpu); WRITE_ONCE(nohz.needs_update, 1); out: /* * Each time a cpu enter idle, we assume that it has blocked load and * enable the periodic update of the load of idle cpus */ WRITE_ONCE(nohz.has_blocked, 1); } static bool update_nohz_stats(struct rq *rq) { unsigned int cpu = rq->cpu; if (!rq->has_blocked_load) return false; if (!cpumask_test_cpu(cpu, nohz.idle_cpus_mask)) return false; if (!time_after(jiffies, READ_ONCE(rq->last_blocked_load_update_tick))) return true; update_blocked_averages(cpu); return rq->has_blocked_load; } /* * Internal function that runs load balance for all idle cpus. The load balance * can be a simple update of blocked load or a complete load balance with * tasks movement depending of flags. */ static void _nohz_idle_balance(struct rq *this_rq, unsigned int flags) { /* Earliest time when we have to do rebalance again */ unsigned long now = jiffies; unsigned long next_balance = now + 60*HZ; bool has_blocked_load = false; int update_next_balance = 0; int this_cpu = this_rq->cpu; int balance_cpu; struct rq *rq; SCHED_WARN_ON((flags & NOHZ_KICK_MASK) == NOHZ_BALANCE_KICK); /* * We assume there will be no idle load after this update and clear * the has_blocked flag. If a cpu enters idle in the mean time, it will * set the has_blocked flag and trigger another update of idle load. * Because a cpu that becomes idle, is added to idle_cpus_mask before * setting the flag, we are sure to not clear the state and not * check the load of an idle cpu. * * Same applies to idle_cpus_mask vs needs_update. */ if (flags & NOHZ_STATS_KICK) WRITE_ONCE(nohz.has_blocked, 0); if (flags & NOHZ_NEXT_KICK) WRITE_ONCE(nohz.needs_update, 0); /* * Ensures that if we miss the CPU, we must see the has_blocked * store from nohz_balance_enter_idle(). */ smp_mb(); /* * Start with the next CPU after this_cpu so we will end with this_cpu and let a * chance for other idle cpu to pull load. */ for_each_cpu_wrap(balance_cpu, nohz.idle_cpus_mask, this_cpu+1) { if (!idle_cpu(balance_cpu)) continue; /* * If this CPU gets work to do, stop the load balancing * work being done for other CPUs. Next load * balancing owner will pick it up. */ if (need_resched()) { if (flags & NOHZ_STATS_KICK) has_blocked_load = true; if (flags & NOHZ_NEXT_KICK) WRITE_ONCE(nohz.needs_update, 1); goto abort; } rq = cpu_rq(balance_cpu); if (flags & NOHZ_STATS_KICK) has_blocked_load |= update_nohz_stats(rq); /* * If time for next balance is due, * do the balance. */ if (time_after_eq(jiffies, rq->next_balance)) { struct rq_flags rf; rq_lock_irqsave(rq, &rf); update_rq_clock(rq); rq_unlock_irqrestore(rq, &rf); if (flags & NOHZ_BALANCE_KICK) rebalance_domains(rq, CPU_IDLE); } if (time_after(next_balance, rq->next_balance)) { next_balance = rq->next_balance; update_next_balance = 1; } } /* * next_balance will be updated only when there is a need. * When the CPU is attached to null domain for ex, it will not be * updated. */ if (likely(update_next_balance)) nohz.next_balance = next_balance; if (flags & NOHZ_STATS_KICK) WRITE_ONCE(nohz.next_blocked, now + msecs_to_jiffies(LOAD_AVG_PERIOD)); abort: /* There is still blocked load, enable periodic update */ if (has_blocked_load) WRITE_ONCE(nohz.has_blocked, 1); } /* * In CONFIG_NO_HZ_COMMON case, the idle balance kickee will do the * rebalancing for all the cpus for whom scheduler ticks are stopped. */ static bool nohz_idle_balance(struct rq *this_rq, enum cpu_idle_type idle) { unsigned int flags = this_rq->nohz_idle_balance; if (!flags) return false; this_rq->nohz_idle_balance = 0; if (idle != CPU_IDLE) return false; _nohz_idle_balance(this_rq, flags); return true; } /* * Check if we need to directly run the ILB for updating blocked load before * entering idle state. Here we run ILB directly without issuing IPIs. * * Note that when this function is called, the tick may not yet be stopped on * this CPU yet. nohz.idle_cpus_mask is updated only when tick is stopped and * cleared on the next busy tick. In other words, nohz.idle_cpus_mask updates * don't align with CPUs enter/exit idle to avoid bottlenecks due to high idle * entry/exit rate (usec). So it is possible that _nohz_idle_balance() is * called from this function on (this) CPU that's not yet in the mask. That's * OK because the goal of nohz_run_idle_balance() is to run ILB only for * updating the blocked load of already idle CPUs without waking up one of * those idle CPUs and outside the preempt disable / irq off phase of the local * cpu about to enter idle, because it can take a long time. */ void nohz_run_idle_balance(int cpu) { unsigned int flags; flags = atomic_fetch_andnot(NOHZ_NEWILB_KICK, nohz_flags(cpu)); /* * Update the blocked load only if no SCHED_SOFTIRQ is about to happen * (ie NOHZ_STATS_KICK set) and will do the same. */ if ((flags == NOHZ_NEWILB_KICK) && !need_resched()) _nohz_idle_balance(cpu_rq(cpu), NOHZ_STATS_KICK); } static void nohz_newidle_balance(struct rq *this_rq) { int this_cpu = this_rq->cpu; /* * This CPU doesn't want to be disturbed by scheduler * housekeeping */ if (!housekeeping_cpu(this_cpu, HK_TYPE_SCHED)) return; /* Will wake up very soon. No time for doing anything else*/ if (this_rq->avg_idle < sysctl_sched_migration_cost) return; /* Don't need to update blocked load of idle CPUs*/ if (!READ_ONCE(nohz.has_blocked) || time_before(jiffies, READ_ONCE(nohz.next_blocked))) return; /* * Set the need to trigger ILB in order to update blocked load * before entering idle state. */ atomic_or(NOHZ_NEWILB_KICK, nohz_flags(this_cpu)); } #else /* !CONFIG_NO_HZ_COMMON */ static inline void nohz_balancer_kick(struct rq *rq) { } static inline bool nohz_idle_balance(struct rq *this_rq, enum cpu_idle_type idle) { return false; } static inline void nohz_newidle_balance(struct rq *this_rq) { } #endif /* CONFIG_NO_HZ_COMMON */ /* * newidle_balance is called by schedule() if this_cpu is about to become * idle. Attempts to pull tasks from other CPUs. * * Returns: * < 0 - we released the lock and there are !fair tasks present * 0 - failed, no new tasks * > 0 - success, new (fair) tasks present */ static int newidle_balance(struct rq *this_rq, struct rq_flags *rf) { unsigned long next_balance = jiffies + HZ; int this_cpu = this_rq->cpu; u64 t0, t1, curr_cost = 0; struct sched_domain *sd; int pulled_task = 0; update_misfit_status(NULL, this_rq); /* * There is a task waiting to run. No need to search for one. * Return 0; the task will be enqueued when switching to idle. */ if (this_rq->ttwu_pending) return 0; /* * We must set idle_stamp _before_ calling idle_balance(), such that we * measure the duration of idle_balance() as idle time. */ this_rq->idle_stamp = rq_clock(this_rq); /* * Do not pull tasks towards !active CPUs... */ if (!cpu_active(this_cpu)) return 0; /* * This is OK, because current is on_cpu, which avoids it being picked * for load-balance and preemption/IRQs are still disabled avoiding * further scheduler activity on it and we're being very careful to * re-start the picking loop. */ rq_unpin_lock(this_rq, rf); rcu_read_lock(); sd = rcu_dereference_check_sched_domain(this_rq->sd); if (!READ_ONCE(this_rq->rd->overload) || (sd && this_rq->avg_idle < sd->max_newidle_lb_cost)) { if (sd) update_next_balance(sd, &next_balance); rcu_read_unlock(); goto out; } rcu_read_unlock(); raw_spin_rq_unlock(this_rq); t0 = sched_clock_cpu(this_cpu); update_blocked_averages(this_cpu); rcu_read_lock(); for_each_domain(this_cpu, sd) { int continue_balancing = 1; u64 domain_cost; update_next_balance(sd, &next_balance); if (this_rq->avg_idle < curr_cost + sd->max_newidle_lb_cost) break; if (sd->flags & SD_BALANCE_NEWIDLE) { pulled_task = load_balance(this_cpu, this_rq, sd, CPU_NEWLY_IDLE, &continue_balancing); t1 = sched_clock_cpu(this_cpu); domain_cost = t1 - t0; update_newidle_cost(sd, domain_cost); curr_cost += domain_cost; t0 = t1; } /* * Stop searching for tasks to pull if there are * now runnable tasks on this rq. */ if (pulled_task || this_rq->nr_running > 0 || this_rq->ttwu_pending) break; } rcu_read_unlock(); raw_spin_rq_lock(this_rq); if (curr_cost > this_rq->max_idle_balance_cost) this_rq->max_idle_balance_cost = curr_cost; /* * While browsing the domains, we released the rq lock, a task could * have been enqueued in the meantime. Since we're not going idle, * pretend we pulled a task. */ if (this_rq->cfs.h_nr_running && !pulled_task) pulled_task = 1; /* Is there a task of a high priority class? */ if (this_rq->nr_running != this_rq->cfs.h_nr_running) pulled_task = -1; out: /* Move the next balance forward */ if (time_after(this_rq->next_balance, next_balance)) this_rq->next_balance = next_balance; if (pulled_task) this_rq->idle_stamp = 0; else nohz_newidle_balance(this_rq); rq_repin_lock(this_rq, rf); return pulled_task; } /* * run_rebalance_domains is triggered when needed from the scheduler tick. * Also triggered for nohz idle balancing (with nohz_balancing_kick set). */ static __latent_entropy void run_rebalance_domains(struct softirq_action *h) { struct rq *this_rq = this_rq(); enum cpu_idle_type idle = this_rq->idle_balance ? CPU_IDLE : CPU_NOT_IDLE; /* * If this CPU has a pending nohz_balance_kick, then do the * balancing on behalf of the other idle CPUs whose ticks are * stopped. Do nohz_idle_balance *before* rebalance_domains to * give the idle CPUs a chance to load balance. Else we may * load balance only within the local sched_domain hierarchy * and abort nohz_idle_balance altogether if we pull some load. */ if (nohz_idle_balance(this_rq, idle)) return; /* normal load balance */ update_blocked_averages(this_rq->cpu); rebalance_domains(this_rq, idle); } /* * Trigger the SCHED_SOFTIRQ if it is time to do periodic load balancing. */ void trigger_load_balance(struct rq *rq) { /* * Don't need to rebalance while attached to NULL domain or * runqueue CPU is not active */ if (unlikely(on_null_domain(rq) || !cpu_active(cpu_of(rq)))) return; if (time_after_eq(jiffies, rq->next_balance)) raise_softirq(SCHED_SOFTIRQ); nohz_balancer_kick(rq); } static void rq_online_fair(struct rq *rq) { update_sysctl(); update_runtime_enabled(rq); } static void rq_offline_fair(struct rq *rq) { update_sysctl(); /* Ensure any throttled groups are reachable by pick_next_task */ unthrottle_offline_cfs_rqs(rq); } #endif /* CONFIG_SMP */ #ifdef CONFIG_SCHED_CORE static inline bool __entity_slice_used(struct sched_entity *se, int min_nr_tasks) { u64 rtime = se->sum_exec_runtime - se->prev_sum_exec_runtime; u64 slice = se->slice; return (rtime * min_nr_tasks > slice); } #define MIN_NR_TASKS_DURING_FORCEIDLE 2 static inline void task_tick_core(struct rq *rq, struct task_struct *curr) { if (!sched_core_enabled(rq)) return; /* * If runqueue has only one task which used up its slice and * if the sibling is forced idle, then trigger schedule to * give forced idle task a chance. * * sched_slice() considers only this active rq and it gets the * whole slice. But during force idle, we have siblings acting * like a single runqueue and hence we need to consider runnable * tasks on this CPU and the forced idle CPU. Ideally, we should * go through the forced idle rq, but that would be a perf hit. * We can assume that the forced idle CPU has at least * MIN_NR_TASKS_DURING_FORCEIDLE - 1 tasks and use that to check * if we need to give up the CPU. */ if (rq->core->core_forceidle_count && rq->cfs.nr_running == 1 && __entity_slice_used(&curr->se, MIN_NR_TASKS_DURING_FORCEIDLE)) resched_curr(rq); } /* * se_fi_update - Update the cfs_rq->min_vruntime_fi in a CFS hierarchy if needed. */ static void se_fi_update(const struct sched_entity *se, unsigned int fi_seq, bool forceidle) { for_each_sched_entity(se) { struct cfs_rq *cfs_rq = cfs_rq_of(se); if (forceidle) { if (cfs_rq->forceidle_seq == fi_seq) break; cfs_rq->forceidle_seq = fi_seq; } cfs_rq->min_vruntime_fi = cfs_rq->min_vruntime; } } void task_vruntime_update(struct rq *rq, struct task_struct *p, bool in_fi) { struct sched_entity *se = &p->se; if (p->sched_class != &fair_sched_class) return; se_fi_update(se, rq->core->core_forceidle_seq, in_fi); } bool cfs_prio_less(const struct task_struct *a, const struct task_struct *b, bool in_fi) { struct rq *rq = task_rq(a); const struct sched_entity *sea = &a->se; const struct sched_entity *seb = &b->se; struct cfs_rq *cfs_rqa; struct cfs_rq *cfs_rqb; s64 delta; SCHED_WARN_ON(task_rq(b)->core != rq->core); #ifdef CONFIG_FAIR_GROUP_SCHED /* * Find an se in the hierarchy for tasks a and b, such that the se's * are immediate siblings. */ while (sea->cfs_rq->tg != seb->cfs_rq->tg) { int sea_depth = sea->depth; int seb_depth = seb->depth; if (sea_depth >= seb_depth) sea = parent_entity(sea); if (sea_depth <= seb_depth) seb = parent_entity(seb); } se_fi_update(sea, rq->core->core_forceidle_seq, in_fi); se_fi_update(seb, rq->core->core_forceidle_seq, in_fi); cfs_rqa = sea->cfs_rq; cfs_rqb = seb->cfs_rq; #else cfs_rqa = &task_rq(a)->cfs; cfs_rqb = &task_rq(b)->cfs; #endif /* * Find delta after normalizing se's vruntime with its cfs_rq's * min_vruntime_fi, which would have been updated in prior calls * to se_fi_update(). */ delta = (s64)(sea->vruntime - seb->vruntime) + (s64)(cfs_rqb->min_vruntime_fi - cfs_rqa->min_vruntime_fi); return delta > 0; } static int task_is_throttled_fair(struct task_struct *p, int cpu) { struct cfs_rq *cfs_rq; #ifdef CONFIG_FAIR_GROUP_SCHED cfs_rq = task_group(p)->cfs_rq[cpu]; #else cfs_rq = &cpu_rq(cpu)->cfs; #endif return throttled_hierarchy(cfs_rq); } #else static inline void task_tick_core(struct rq *rq, struct task_struct *curr) {} #endif /* * scheduler tick hitting a task of our scheduling class. * * NOTE: This function can be called remotely by the tick offload that * goes along full dynticks. Therefore no local assumption can be made * and everything must be accessed through the @rq and @curr passed in * parameters. */ static void task_tick_fair(struct rq *rq, struct task_struct *curr, int queued) { struct cfs_rq *cfs_rq; struct sched_entity *se = &curr->se; for_each_sched_entity(se) { cfs_rq = cfs_rq_of(se); entity_tick(cfs_rq, se, queued); } if (static_branch_unlikely(&sched_numa_balancing)) task_tick_numa(rq, curr); update_misfit_status(curr, rq); update_overutilized_status(task_rq(curr)); task_tick_core(rq, curr); } /* * called on fork with the child task as argument from the parent's context * - child not yet on the tasklist * - preemption disabled */ static void task_fork_fair(struct task_struct *p) { struct sched_entity *se = &p->se, *curr; struct cfs_rq *cfs_rq; struct rq *rq = this_rq(); struct rq_flags rf; rq_lock(rq, &rf); update_rq_clock(rq); cfs_rq = task_cfs_rq(current); curr = cfs_rq->curr; if (curr) update_curr(cfs_rq); place_entity(cfs_rq, se, ENQUEUE_INITIAL); rq_unlock(rq, &rf); } /* * Priority of the task has changed. Check to see if we preempt * the current task. */ static void prio_changed_fair(struct rq *rq, struct task_struct *p, int oldprio) { if (!task_on_rq_queued(p)) return; if (rq->cfs.nr_running == 1) return; /* * Reschedule if we are currently running on this runqueue and * our priority decreased, or if we are not currently running on * this runqueue and our priority is higher than the current's */ if (task_current(rq, p)) { if (p->prio > oldprio) resched_curr(rq); } else wakeup_preempt(rq, p, 0); } #ifdef CONFIG_FAIR_GROUP_SCHED /* * Propagate the changes of the sched_entity across the tg tree to make it * visible to the root */ static void propagate_entity_cfs_rq(struct sched_entity *se) { struct cfs_rq *cfs_rq = cfs_rq_of(se); if (cfs_rq_throttled(cfs_rq)) return; if (!throttled_hierarchy(cfs_rq)) list_add_leaf_cfs_rq(cfs_rq); /* Start to propagate at parent */ se = se->parent; for_each_sched_entity(se) { cfs_rq = cfs_rq_of(se); update_load_avg(cfs_rq, se, UPDATE_TG); if (cfs_rq_throttled(cfs_rq)) break; if (!throttled_hierarchy(cfs_rq)) list_add_leaf_cfs_rq(cfs_rq); } } #else static void propagate_entity_cfs_rq(struct sched_entity *se) { } #endif static void detach_entity_cfs_rq(struct sched_entity *se) { struct cfs_rq *cfs_rq = cfs_rq_of(se); #ifdef CONFIG_SMP /* * In case the task sched_avg hasn't been attached: * - A forked task which hasn't been woken up by wake_up_new_task(). * - A task which has been woken up by try_to_wake_up() but is * waiting for actually being woken up by sched_ttwu_pending(). */ if (!se->avg.last_update_time) return; #endif /* Catch up with the cfs_rq and remove our load when we leave */ update_load_avg(cfs_rq, se, 0); detach_entity_load_avg(cfs_rq, se); update_tg_load_avg(cfs_rq); propagate_entity_cfs_rq(se); } static void attach_entity_cfs_rq(struct sched_entity *se) { struct cfs_rq *cfs_rq = cfs_rq_of(se); /* Synchronize entity with its cfs_rq */ update_load_avg(cfs_rq, se, sched_feat(ATTACH_AGE_LOAD) ? 0 : SKIP_AGE_LOAD); attach_entity_load_avg(cfs_rq, se); update_tg_load_avg(cfs_rq); propagate_entity_cfs_rq(se); } static void detach_task_cfs_rq(struct task_struct *p) { struct sched_entity *se = &p->se; detach_entity_cfs_rq(se); } static void attach_task_cfs_rq(struct task_struct *p) { struct sched_entity *se = &p->se; attach_entity_cfs_rq(se); } static void switched_from_fair(struct rq *rq, struct task_struct *p) { detach_task_cfs_rq(p); } static void switched_to_fair(struct rq *rq, struct task_struct *p) { attach_task_cfs_rq(p); if (task_on_rq_queued(p)) { /* * We were most likely switched from sched_rt, so * kick off the schedule if running, otherwise just see * if we can still preempt the current task. */ if (task_current(rq, p)) resched_curr(rq); else wakeup_preempt(rq, p, 0); } } /* Account for a task changing its policy or group. * * This routine is mostly called to set cfs_rq->curr field when a task * migrates between groups/classes. */ static void set_next_task_fair(struct rq *rq, struct task_struct *p, bool first) { struct sched_entity *se = &p->se; #ifdef CONFIG_SMP if (task_on_rq_queued(p)) { /* * Move the next running task to the front of the list, so our * cfs_tasks list becomes MRU one. */ list_move(&se->group_node, &rq->cfs_tasks); } #endif for_each_sched_entity(se) { struct cfs_rq *cfs_rq = cfs_rq_of(se); set_next_entity(cfs_rq, se); /* ensure bandwidth has been allocated on our new cfs_rq */ account_cfs_rq_runtime(cfs_rq, 0); } } void init_cfs_rq(struct cfs_rq *cfs_rq) { cfs_rq->tasks_timeline = RB_ROOT_CACHED; u64_u32_store(cfs_rq->min_vruntime, (u64)(-(1LL << 20))); #ifdef CONFIG_SMP raw_spin_lock_init(&cfs_rq->removed.lock); #endif } #ifdef CONFIG_FAIR_GROUP_SCHED static void task_change_group_fair(struct task_struct *p) { /* * We couldn't detach or attach a forked task which * hasn't been woken up by wake_up_new_task(). */ if (READ_ONCE(p->__state) == TASK_NEW) return; detach_task_cfs_rq(p); #ifdef CONFIG_SMP /* Tell se's cfs_rq has been changed -- migrated */ p->se.avg.last_update_time = 0; #endif set_task_rq(p, task_cpu(p)); attach_task_cfs_rq(p); } void free_fair_sched_group(struct task_group *tg) { int i; for_each_possible_cpu(i) { if (tg->cfs_rq) kfree(tg->cfs_rq[i]); if (tg->se) kfree(tg->se[i]); } kfree(tg->cfs_rq); kfree(tg->se); } int alloc_fair_sched_group(struct task_group *tg, struct task_group *parent) { struct sched_entity *se; struct cfs_rq *cfs_rq; int i; tg->cfs_rq = kcalloc(nr_cpu_ids, sizeof(cfs_rq), GFP_KERNEL); if (!tg->cfs_rq) goto err; tg->se = kcalloc(nr_cpu_ids, sizeof(se), GFP_KERNEL); if (!tg->se) goto err; tg->shares = NICE_0_LOAD; init_cfs_bandwidth(tg_cfs_bandwidth(tg), tg_cfs_bandwidth(parent)); for_each_possible_cpu(i) { cfs_rq = kzalloc_node(sizeof(struct cfs_rq), GFP_KERNEL, cpu_to_node(i)); if (!cfs_rq) goto err; se = kzalloc_node(sizeof(struct sched_entity_stats), GFP_KERNEL, cpu_to_node(i)); if (!se) goto err_free_rq; init_cfs_rq(cfs_rq); init_tg_cfs_entry(tg, cfs_rq, se, i, parent->se[i]); init_entity_runnable_average(se); } return 1; err_free_rq: kfree(cfs_rq); err: return 0; } void online_fair_sched_group(struct task_group *tg) { struct sched_entity *se; struct rq_flags rf; struct rq *rq; int i; for_each_possible_cpu(i) { rq = cpu_rq(i); se = tg->se[i]; rq_lock_irq(rq, &rf); update_rq_clock(rq); attach_entity_cfs_rq(se); sync_throttle(tg, i); rq_unlock_irq(rq, &rf); } } void unregister_fair_sched_group(struct task_group *tg) { unsigned long flags; struct rq *rq; int cpu; destroy_cfs_bandwidth(tg_cfs_bandwidth(tg)); for_each_possible_cpu(cpu) { if (tg->se[cpu]) remove_entity_load_avg(tg->se[cpu]); /* * Only empty task groups can be destroyed; so we can speculatively * check on_list without danger of it being re-added. */ if (!tg->cfs_rq[cpu]->on_list) continue; rq = cpu_rq(cpu); raw_spin_rq_lock_irqsave(rq, flags); list_del_leaf_cfs_rq(tg->cfs_rq[cpu]); raw_spin_rq_unlock_irqrestore(rq, flags); } } void init_tg_cfs_entry(struct task_group *tg, struct cfs_rq *cfs_rq, struct sched_entity *se, int cpu, struct sched_entity *parent) { struct rq *rq = cpu_rq(cpu); cfs_rq->tg = tg; cfs_rq->rq = rq; init_cfs_rq_runtime(cfs_rq); tg->cfs_rq[cpu] = cfs_rq; tg->se[cpu] = se; /* se could be NULL for root_task_group */ if (!se) return; if (!parent) { se->cfs_rq = &rq->cfs; se->depth = 0; } else { se->cfs_rq = parent->my_q; se->depth = parent->depth + 1; } se->my_q = cfs_rq; /* guarantee group entities always have weight */ update_load_set(&se->load, NICE_0_LOAD); se->parent = parent; } static DEFINE_MUTEX(shares_mutex); static int __sched_group_set_shares(struct task_group *tg, unsigned long shares) { int i; lockdep_assert_held(&shares_mutex); /* * We can't change the weight of the root cgroup. */ if (!tg->se[0]) return -EINVAL; shares = clamp(shares, scale_load(MIN_SHARES), scale_load(MAX_SHARES)); if (tg->shares == shares) return 0; tg->shares = shares; for_each_possible_cpu(i) { struct rq *rq = cpu_rq(i); struct sched_entity *se = tg->se[i]; struct rq_flags rf; /* Propagate contribution to hierarchy */ rq_lock_irqsave(rq, &rf); update_rq_clock(rq); for_each_sched_entity(se) { update_load_avg(cfs_rq_of(se), se, UPDATE_TG); update_cfs_group(se); } rq_unlock_irqrestore(rq, &rf); } return 0; } int sched_group_set_shares(struct task_group *tg, unsigned long shares) { int ret; mutex_lock(&shares_mutex); if (tg_is_idle(tg)) ret = -EINVAL; else ret = __sched_group_set_shares(tg, shares); mutex_unlock(&shares_mutex); return ret; } int sched_group_set_idle(struct task_group *tg, long idle) { int i; if (tg == &root_task_group) return -EINVAL; if (idle < 0 || idle > 1) return -EINVAL; mutex_lock(&shares_mutex); if (tg->idle == idle) { mutex_unlock(&shares_mutex); return 0; } tg->idle = idle; for_each_possible_cpu(i) { struct rq *rq = cpu_rq(i); struct sched_entity *se = tg->se[i]; struct cfs_rq *parent_cfs_rq, *grp_cfs_rq = tg->cfs_rq[i]; bool was_idle = cfs_rq_is_idle(grp_cfs_rq); long idle_task_delta; struct rq_flags rf; rq_lock_irqsave(rq, &rf); grp_cfs_rq->idle = idle; if (WARN_ON_ONCE(was_idle == cfs_rq_is_idle(grp_cfs_rq))) goto next_cpu; if (se->on_rq) { parent_cfs_rq = cfs_rq_of(se); if (cfs_rq_is_idle(grp_cfs_rq)) parent_cfs_rq->idle_nr_running++; else parent_cfs_rq->idle_nr_running--; } idle_task_delta = grp_cfs_rq->h_nr_running - grp_cfs_rq->idle_h_nr_running; if (!cfs_rq_is_idle(grp_cfs_rq)) idle_task_delta *= -1; for_each_sched_entity(se) { struct cfs_rq *cfs_rq = cfs_rq_of(se); if (!se->on_rq) break; cfs_rq->idle_h_nr_running += idle_task_delta; /* Already accounted at parent level and above. */ if (cfs_rq_is_idle(cfs_rq)) break; } next_cpu: rq_unlock_irqrestore(rq, &rf); } /* Idle groups have minimum weight. */ if (tg_is_idle(tg)) __sched_group_set_shares(tg, scale_load(WEIGHT_IDLEPRIO)); else __sched_group_set_shares(tg, NICE_0_LOAD); mutex_unlock(&shares_mutex); return 0; } #else /* CONFIG_FAIR_GROUP_SCHED */ void free_fair_sched_group(struct task_group *tg) { } int alloc_fair_sched_group(struct task_group *tg, struct task_group *parent) { return 1; } void online_fair_sched_group(struct task_group *tg) { } void unregister_fair_sched_group(struct task_group *tg) { } #endif /* CONFIG_FAIR_GROUP_SCHED */ static unsigned int get_rr_interval_fair(struct rq *rq, struct task_struct *task) { struct sched_entity *se = &task->se; unsigned int rr_interval = 0; /* * Time slice is 0 for SCHED_OTHER tasks that are on an otherwise * idle runqueue: */ if (rq->cfs.load.weight) rr_interval = NS_TO_JIFFIES(se->slice); return rr_interval; } /* * All the scheduling class methods: */ DEFINE_SCHED_CLASS(fair) = { .enqueue_task = enqueue_task_fair, .dequeue_task = dequeue_task_fair, .yield_task = yield_task_fair, .yield_to_task = yield_to_task_fair, .wakeup_preempt = check_preempt_wakeup_fair, .pick_next_task = __pick_next_task_fair, .put_prev_task = put_prev_task_fair, .set_next_task = set_next_task_fair, #ifdef CONFIG_SMP .balance = balance_fair, .pick_task = pick_task_fair, .select_task_rq = select_task_rq_fair, .migrate_task_rq = migrate_task_rq_fair, .rq_online = rq_online_fair, .rq_offline = rq_offline_fair, .task_dead = task_dead_fair, .set_cpus_allowed = set_cpus_allowed_common, #endif .task_tick = task_tick_fair, .task_fork = task_fork_fair, .prio_changed = prio_changed_fair, .switched_from = switched_from_fair, .switched_to = switched_to_fair, .get_rr_interval = get_rr_interval_fair, .update_curr = update_curr_fair, #ifdef CONFIG_FAIR_GROUP_SCHED .task_change_group = task_change_group_fair, #endif #ifdef CONFIG_SCHED_CORE .task_is_throttled = task_is_throttled_fair, #endif #ifdef CONFIG_UCLAMP_TASK .uclamp_enabled = 1, #endif }; #ifdef CONFIG_SCHED_DEBUG void print_cfs_stats(struct seq_file *m, int cpu) { struct cfs_rq *cfs_rq, *pos; rcu_read_lock(); for_each_leaf_cfs_rq_safe(cpu_rq(cpu), cfs_rq, pos) print_cfs_rq(m, cpu, cfs_rq); rcu_read_unlock(); } #ifdef CONFIG_NUMA_BALANCING void show_numa_stats(struct task_struct *p, struct seq_file *m) { int node; unsigned long tsf = 0, tpf = 0, gsf = 0, gpf = 0; struct numa_group *ng; rcu_read_lock(); ng = rcu_dereference(p->numa_group); for_each_online_node(node) { if (p->numa_faults) { tsf = p->numa_faults[task_faults_idx(NUMA_MEM, node, 0)]; tpf = p->numa_faults[task_faults_idx(NUMA_MEM, node, 1)]; } if (ng) { gsf = ng->faults[task_faults_idx(NUMA_MEM, node, 0)], gpf = ng->faults[task_faults_idx(NUMA_MEM, node, 1)]; } print_numa_stats(m, node, tsf, tpf, gsf, gpf); } rcu_read_unlock(); } #endif /* CONFIG_NUMA_BALANCING */ #endif /* CONFIG_SCHED_DEBUG */ __init void init_sched_fair_class(void) { #ifdef CONFIG_SMP int i; for_each_possible_cpu(i) { zalloc_cpumask_var_node(&per_cpu(load_balance_mask, i), GFP_KERNEL, cpu_to_node(i)); zalloc_cpumask_var_node(&per_cpu(select_rq_mask, i), GFP_KERNEL, cpu_to_node(i)); zalloc_cpumask_var_node(&per_cpu(should_we_balance_tmpmask, i), GFP_KERNEL, cpu_to_node(i)); #ifdef CONFIG_CFS_BANDWIDTH INIT_CSD(&cpu_rq(i)->cfsb_csd, __cfsb_csd_unthrottle, cpu_rq(i)); INIT_LIST_HEAD(&cpu_rq(i)->cfsb_csd_list); #endif } open_softirq(SCHED_SOFTIRQ, run_rebalance_domains); #ifdef CONFIG_NO_HZ_COMMON nohz.next_balance = jiffies; nohz.next_blocked = jiffies; zalloc_cpumask_var(&nohz.idle_cpus_mask, GFP_NOWAIT); #endif #endif /* SMP */ }
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