| Author | Tokens | Token Proportion | Commits | Commit Proportion |
|---|---|---|---|---|
| Peter Zijlstra | 14922 | 42.79% | 218 | 28.65% |
| Rik Van Riel | 2991 | 8.58% | 52 | 6.83% |
| Vincent Guittot | 2691 | 7.72% | 45 | 5.91% |
| Mel Gorman | 2468 | 7.08% | 40 | 5.26% |
| Paul Turner | 2334 | 6.69% | 32 | 4.20% |
| Ingo Molnar | 1062 | 3.05% | 38 | 4.99% |
| Srikar Dronamraju | 704 | 2.02% | 24 | 3.15% |
| Yuyang Du | 564 | 1.62% | 11 | 1.45% |
| Patrick Bellasi | 541 | 1.55% | 5 | 0.66% |
| Morten Rasmussen | 504 | 1.45% | 10 | 1.31% |
| Josh Poimboeuf | 467 | 1.34% | 4 | 0.53% |
| Byungchul Park | 425 | 1.22% | 9 | 1.18% |
| JoonSoo Kim | 399 | 1.14% | 9 | 1.18% |
| Kirill Tkhai | 384 | 1.10% | 9 | 1.18% |
| Mike Galbraith | 369 | 1.06% | 24 | 3.15% |
| Frédéric Weisbecker | 240 | 0.69% | 11 | 1.45% |
| Srivatsa Vaddagiri | 227 | 0.65% | 11 | 1.45% |
| Nico Pitre | 203 | 0.58% | 5 | 0.66% |
| Jason Low | 201 | 0.58% | 6 | 0.79% |
| Michael Neuling | 200 | 0.57% | 1 | 0.13% |
| Brendan Jackman | 198 | 0.57% | 5 | 0.66% |
| Suresh B. Siddha | 176 | 0.50% | 8 | 1.05% |
| Vladimir Davydov | 139 | 0.40% | 5 | 0.66% |
| Viresh Kumar | 136 | 0.39% | 8 | 1.05% |
| Venkatesh Pallipadi | 132 | 0.38% | 4 | 0.53% |
| Tejun Heo | 118 | 0.34% | 3 | 0.39% |
| Tim Chen | 114 | 0.33% | 3 | 0.39% |
| Iulia Manda | 114 | 0.33% | 1 | 0.13% |
| Ben Segall | 112 | 0.32% | 7 | 0.92% |
| Joonwoo Park | 105 | 0.30% | 1 | 0.13% |
| Paul Gortmaker | 84 | 0.24% | 1 | 0.13% |
| Josef Bacik | 77 | 0.22% | 1 | 0.13% |
| Phil Auld | 77 | 0.22% | 1 | 0.13% |
| Michael Wang | 72 | 0.21% | 5 | 0.66% |
| Christian Ehrhardt | 69 | 0.20% | 3 | 0.39% |
| Peter Williams | 67 | 0.19% | 4 | 0.53% |
| Xunlei Pang | 62 | 0.18% | 4 | 0.53% |
| Alex Shi | 60 | 0.17% | 6 | 0.79% |
| Konstantin Khlebnikov | 57 | 0.16% | 2 | 0.26% |
| Linus Torvalds | 56 | 0.16% | 3 | 0.39% |
| Steven Rostedt | 52 | 0.15% | 2 | 0.26% |
| Nikhil P Rao | 47 | 0.13% | 3 | 0.39% |
| Wanpeng Li | 47 | 0.13% | 4 | 0.53% |
| Gregory Haskins | 39 | 0.11% | 2 | 0.26% |
| Davidlohr Bueso A | 37 | 0.11% | 1 | 0.13% |
| Fabio Checconi | 33 | 0.09% | 1 | 0.13% |
| Steve Muckle | 32 | 0.09% | 4 | 0.53% |
| Daniel Lezcano | 32 | 0.09% | 6 | 0.79% |
| Lucas De Marchi | 31 | 0.09% | 2 | 0.26% |
| Stanislaw Gruszka | 29 | 0.08% | 1 | 0.13% |
| Uladzislau Rezki | 29 | 0.08% | 1 | 0.13% |
| Matt Fleming | 27 | 0.08% | 3 | 0.39% |
| Kirill V Tkhai | 26 | 0.07% | 2 | 0.26% |
| Daniel Axtens | 26 | 0.07% | 1 | 0.13% |
| Arjan van de Ven | 23 | 0.07% | 3 | 0.39% |
| Darren Hart | 19 | 0.05% | 1 | 0.13% |
| Quentin Perret | 18 | 0.05% | 1 | 0.13% |
| Rafael J. Wysocki | 18 | 0.05% | 2 | 0.26% |
| Bharata B Rao | 18 | 0.05% | 2 | 0.26% |
| Prashanth Nageshappa | 17 | 0.05% | 2 | 0.26% |
| Oleg Nesterov | 17 | 0.05% | 1 | 0.13% |
| Dietmar Eggemann | 16 | 0.05% | 5 | 0.66% |
| Ken Chen | 15 | 0.04% | 2 | 0.26% |
| Jeffrey Hugo | 15 | 0.04% | 1 | 0.13% |
| Lin Ming | 13 | 0.04% | 2 | 0.26% |
| Hillf Danton | 13 | 0.04% | 1 | 0.13% |
| Daisuke Nishimura | 13 | 0.04% | 1 | 0.13% |
| Wang Xingchao | 12 | 0.03% | 1 | 0.13% |
| Waiman Long | 12 | 0.03% | 1 | 0.13% |
| Tetsuo Handa | 11 | 0.03% | 1 | 0.13% |
| Yong Zhang | 10 | 0.03% | 1 | 0.13% |
| Hiroshi Shimamoto | 10 | 0.03% | 1 | 0.13% |
| Rohit Jain | 10 | 0.03% | 1 | 0.13% |
| Leo Yan | 9 | 0.03% | 2 | 0.26% |
| Joel Fernandes | 9 | 0.03% | 2 | 0.26% |
| Peter Boonstoppel | 9 | 0.03% | 1 | 0.13% |
| Yao Dongdong | 8 | 0.02% | 1 | 0.13% |
| Jan Beulich | 8 | 0.02% | 2 | 0.26% |
| Thomas Gleixner | 8 | 0.02% | 3 | 0.39% |
| Naoya Horiguchi | 7 | 0.02% | 1 | 0.13% |
| Dmitry Adamushko | 7 | 0.02% | 1 | 0.13% |
| Frank Mayhar | 7 | 0.02% | 1 | 0.13% |
| Boqun Feng | 7 | 0.02% | 1 | 0.13% |
| Vlastimil Babka | 6 | 0.02% | 1 | 0.13% |
| Andrei Epure | 6 | 0.02% | 2 | 0.26% |
| Kees Cook | 6 | 0.02% | 1 | 0.13% |
| Preeti U. Murthy | 6 | 0.02% | 2 | 0.26% |
| Diwakar Tundlam | 6 | 0.02% | 1 | 0.13% |
| Ting Yang | 6 | 0.02% | 1 | 0.13% |
| Christian Engelmayer | 6 | 0.02% | 1 | 0.13% |
| Li Zefan | 6 | 0.02% | 2 | 0.26% |
| Vaidyanathan Srinivasan | 5 | 0.01% | 1 | 0.13% |
| Nicholas Mc Guire | 4 | 0.01% | 1 | 0.13% |
| Harvey Harrison | 4 | 0.01% | 1 | 0.13% |
| Andrey Vagin | 4 | 0.01% | 1 | 0.13% |
| Zhu Yanhai | 4 | 0.01% | 1 | 0.13% |
| Hugh Dickins | 4 | 0.01% | 1 | 0.13% |
| Dhaval Giani | 3 | 0.01% | 1 | 0.13% |
| Randy Dunlap | 3 | 0.01% | 3 | 0.39% |
| Kamalesh Babulal | 3 | 0.01% | 2 | 0.26% |
| Américo Wang | 2 | 0.01% | 1 | 0.13% |
| Stephan Bärwolf | 2 | 0.01% | 1 | 0.13% |
| Balbir Singh | 2 | 0.01% | 1 | 0.13% |
| Norbert Manthey | 2 | 0.01% | 1 | 0.13% |
| Gautham R. Shenoy | 2 | 0.01% | 1 | 0.13% |
| Emese Revfy | 1 | 0.00% | 1 | 0.13% |
| Greg Kroah-Hartman | 1 | 0.00% | 1 | 0.13% |
| Song Muchun | 1 | 0.00% | 1 | 0.13% |
| Ramkumar Ramachandra | 1 | 0.00% | 1 | 0.13% |
| Yacine Belkadi | 1 | 0.00% | 1 | 0.13% |
| Borislav Petkov | 1 | 0.00% | 1 | 0.13% |
| David Shaohua Li | 1 | 0.00% | 1 | 0.13% |
| Masanari Iida | 1 | 0.00% | 1 | 0.13% |
| Marcin Nowakowski | 1 | 0.00% | 1 | 0.13% |
| Arnd Bergmann | 1 | 0.00% | 1 | 0.13% |
| Christoph Lameter | 1 | 0.00% | 1 | 0.13% |
| Adrian Bunk | 1 | 0.00% | 1 | 0.13% |
| Zhihui Zhang | 1 | 0.00% | 1 | 0.13% |
| H Hartley Sweeten | 1 | 0.00% | 1 | 0.13% |
| Andreea-Cristina Bernat | 1 | 0.00% | 1 | 0.13% |
| Paul E. McKenney | 1 | 0.00% | 1 | 0.13% |
| Total | 34875 | 761 |
// 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 "sched.h" #include <trace/events/sched.h> /* * Targeted preemption latency for CPU-bound tasks: * * NOTE: this latency value is not the same as the concept of * 'timeslice length' - timeslices in CFS are of variable length * and have no persistent notion like in traditional, time-slice * based scheduling concepts. * * (to see the precise effective timeslice length of your workload, * run vmstat and monitor the context-switches (cs) field) * * (default: 6ms * (1 + ilog(ncpus)), units: nanoseconds) */ unsigned int sysctl_sched_latency = 6000000ULL; unsigned int normalized_sysctl_sched_latency = 6000000ULL; /* * 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)) */ enum sched_tunable_scaling 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_min_granularity = 750000ULL; unsigned int normalized_sysctl_sched_min_granularity = 750000ULL; /* * This value is kept at sysctl_sched_latency/sysctl_sched_min_granularity */ static unsigned int sched_nr_latency = 8; /* * After fork, child runs first. If set to 0 (default) then * parent will (try to) run first. */ unsigned int sysctl_sched_child_runs_first __read_mostly; /* * SCHED_OTHER wake-up granularity. * * This option delays the preemption effects of decoupled workloads * and reduces their over-scheduling. Synchronous workloads will still * have immediate wakeup/sleep latencies. * * (default: 1 msec * (1 + ilog(ncpus)), units: nanoseconds) */ unsigned int sysctl_sched_wakeup_granularity = 1000000UL; unsigned int normalized_sysctl_sched_wakeup_granularity = 1000000UL; const_debug unsigned int sysctl_sched_migration_cost = 500000UL; #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; } #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) */ unsigned int sysctl_sched_cfs_bandwidth_slice = 5000UL; #endif /* * The margin used when comparing utilization with CPU capacity: * util * margin < capacity * 1024 * * (default: ~20%) */ unsigned int capacity_margin = 1280; 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_min_granularity); SET_SYSCTL(sched_latency); SET_SYSCTL(sched_wakeup_granularity); #undef SET_SYSCTL } void 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); int shift = WMULT_SHIFT; __update_inv_weight(lw); if (unlikely(fact >> 32)) { while (fact >> 32) { fact >>= 1; shift--; } } /* hint to use a 32x32->64 mul */ fact = (u64)(u32)fact * lw->inv_weight; while (fact >> 32) { fact >>= 1; shift--; } return mul_u64_u32_shr(delta_exec, fact, shift); } const struct sched_class fair_sched_class; /************************************************************** * CFS operations on generic schedulable entities: */ #ifdef CONFIG_FAIR_GROUP_SCHED /* cpu runqueue to which this cfs_rq is attached */ static inline struct rq *rq_of(struct cfs_rq *cfs_rq) { return cfs_rq->rq; } static inline struct task_struct *task_of(struct sched_entity *se) { SCHED_WARN_ON(!entity_is_task(se)); return container_of(se, struct task_struct, se); } /* Walk up scheduling entities hierarchy */ #define for_each_sched_entity(se) \ for (; se; se = se->parent) static inline struct cfs_rq *task_cfs_rq(struct task_struct *p) { return p->se.cfs_rq; } /* runqueue on which this entity is (to be) queued */ static inline struct cfs_rq *cfs_rq_of(struct sched_entity *se) { return se->cfs_rq; } /* runqueue "owned" by this group */ static inline struct cfs_rq *group_cfs_rq(struct sched_entity *grp) { return grp->my_q; } static inline void list_add_leaf_cfs_rq(struct cfs_rq *cfs_rq) { if (!cfs_rq->on_list) { struct rq *rq = rq_of(cfs_rq); int cpu = cpu_of(rq); /* * 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 beg 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; } else 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 beg 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; } else { /* * 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 beg 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 beg * of the branch */ rq->tmp_alone_branch = &cfs_rq->leaf_cfs_rq_list; } cfs_rq->on_list = 1; } } static inline void list_del_leaf_cfs_rq(struct cfs_rq *cfs_rq) { if (cfs_rq->on_list) { list_del_rcu(&cfs_rq->leaf_cfs_rq_list); cfs_rq->on_list = 0; } } /* 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(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); } } #else /* !CONFIG_FAIR_GROUP_SCHED */ static inline struct task_struct *task_of(struct sched_entity *se) { return container_of(se, struct task_struct, se); } static inline struct rq *rq_of(struct cfs_rq *cfs_rq) { return container_of(cfs_rq, struct rq, cfs); } #define for_each_sched_entity(se) \ for (; se; se = NULL) static inline struct cfs_rq *task_cfs_rq(struct task_struct *p) { return &task_rq(p)->cfs; } static inline struct cfs_rq *cfs_rq_of(struct sched_entity *se) { struct task_struct *p = task_of(se); struct rq *rq = task_rq(p); return &rq->cfs; } /* runqueue "owned" by this group */ static inline struct cfs_rq *group_cfs_rq(struct sched_entity *grp) { return NULL; } static inline void list_add_leaf_cfs_rq(struct cfs_rq *cfs_rq) { } static inline void list_del_leaf_cfs_rq(struct cfs_rq *cfs_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) { } #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 int entity_before(struct sched_entity *a, struct sched_entity *b) { return (s64)(a->vruntime - b->vruntime) < 0; } static void update_min_vruntime(struct cfs_rq *cfs_rq) { struct sched_entity *curr = cfs_rq->curr; struct rb_node *leftmost = rb_first_cached(&cfs_rq->tasks_timeline); u64 vruntime = cfs_rq->min_vruntime; if (curr) { if (curr->on_rq) vruntime = curr->vruntime; else curr = NULL; } if (leftmost) { /* non-empty tree */ struct sched_entity *se; se = rb_entry(leftmost, struct sched_entity, run_node); if (!curr) vruntime = se->vruntime; else vruntime = min_vruntime(vruntime, se->vruntime); } /* ensure we never gain time by being placed backwards. */ cfs_rq->min_vruntime = max_vruntime(cfs_rq->min_vruntime, vruntime); #ifndef CONFIG_64BIT smp_wmb(); cfs_rq->min_vruntime_copy = cfs_rq->min_vruntime; #endif } /* * Enqueue an entity into the rb-tree: */ static void __enqueue_entity(struct cfs_rq *cfs_rq, struct sched_entity *se) { struct rb_node **link = &cfs_rq->tasks_timeline.rb_root.rb_node; struct rb_node *parent = NULL; struct sched_entity *entry; bool leftmost = true; /* * Find the right place in the rbtree: */ while (*link) { parent = *link; entry = rb_entry(parent, struct sched_entity, run_node); /* * We dont care about collisions. Nodes with * the same key stay together. */ if (entity_before(se, entry)) { link = &parent->rb_left; } else { link = &parent->rb_right; leftmost = false; } } rb_link_node(&se->run_node, parent, link); rb_insert_color_cached(&se->run_node, &cfs_rq->tasks_timeline, leftmost); } static void __dequeue_entity(struct cfs_rq *cfs_rq, struct sched_entity *se) { rb_erase_cached(&se->run_node, &cfs_rq->tasks_timeline); } 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 rb_entry(left, struct sched_entity, run_node); } static struct sched_entity *__pick_next_entity(struct sched_entity *se) { struct rb_node *next = rb_next(&se->run_node); if (!next) return NULL; return rb_entry(next, struct sched_entity, run_node); } #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 rb_entry(last, struct sched_entity, run_node); } /************************************************************** * Scheduling class statistics methods: */ int sched_proc_update_handler(struct ctl_table *table, int write, void __user *buffer, size_t *lenp, loff_t *ppos) { int ret = proc_dointvec_minmax(table, write, buffer, lenp, ppos); unsigned int factor = get_update_sysctl_factor(); if (ret || !write) return ret; sched_nr_latency = DIV_ROUND_UP(sysctl_sched_latency, sysctl_sched_min_granularity); #define WRT_SYSCTL(name) \ (normalized_sysctl_##name = sysctl_##name / (factor)) WRT_SYSCTL(sched_min_granularity); WRT_SYSCTL(sched_latency); WRT_SYSCTL(sched_wakeup_granularity); #undef WRT_SYSCTL return 0; } #endif /* * 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; } /* * The idea is to set a period in which each task runs once. * * When there are too many tasks (sched_nr_latency) we have to stretch * this period because otherwise the slices get too small. * * p = (nr <= nl) ? l : l*nr/nl */ static u64 __sched_period(unsigned long nr_running) { if (unlikely(nr_running > sched_nr_latency)) return nr_running * sysctl_sched_min_granularity; else return sysctl_sched_latency; } /* * We calculate the wall-time slice from the period by taking a part * proportional to the weight. * * s = p*P[w/rw] */ static u64 sched_slice(struct cfs_rq *cfs_rq, struct sched_entity *se) { u64 slice = __sched_period(cfs_rq->nr_running + !se->on_rq); for_each_sched_entity(se) { struct load_weight *load; struct load_weight lw; cfs_rq = cfs_rq_of(se); load = &cfs_rq->load; if (unlikely(!se->on_rq)) { lw = cfs_rq->load; update_load_add(&lw, se->load.weight); load = &lw; } slice = __calc_delta(slice, se->load.weight, load); } return slice; } /* * We calculate the vruntime slice of a to-be-inserted task. * * vs = s/w */ static u64 sched_vslice(struct cfs_rq *cfs_rq, struct sched_entity *se) { return calc_delta_fair(sched_slice(cfs_rq, se), se); } #ifdef CONFIG_SMP #include "pelt.h" #include "sched-pelt.h" static int select_idle_sibling(struct task_struct *p, int prev_cpu, int cpu); static unsigned long task_h_load(struct task_struct *p); /* 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 intialized with full load to be seen as heavy tasks until * they get a chance to stabilize to their real load level. * Group entities are intialized with zero load to reflect the fact that * nothing has been attached to the task group yet. */ if (entity_is_task(se)) sa->runnable_load_avg = sa->load_avg = scale_load_down(se->load.weight); se->runnable_weight = se->load.weight; /* when this task enqueue'ed, it will contribute to its cfs_rq's load_avg */ } static inline u64 cfs_rq_clock_task(struct cfs_rq *cfs_rq); static void attach_entity_cfs_rq(struct sched_entity *se); /* * 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 sched_entity *se) { struct cfs_rq *cfs_rq = cfs_rq_of(se); struct sched_avg *sa = &se->avg; long cpu_scale = arch_scale_cpu_capacity(NULL, cpu_of(rq_of(cfs_rq))); long cap = (long)(cpu_scale - cfs_rq->avg.util_avg) / 2; 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; } } if (entity_is_task(se)) { struct task_struct *p = task_of(se); 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, 0); switched_from_fair(rq, p); * * such that the next switched_to_fair() has the * expected state. */ se->avg.last_update_time = cfs_rq_clock_task(cfs_rq); return; } } attach_entity_cfs_rq(se); } #else /* !CONFIG_SMP */ void init_entity_runnable_average(struct sched_entity *se) { } void post_init_entity_util_avg(struct sched_entity *se) { } static void update_tg_load_avg(struct cfs_rq *cfs_rq, int force) { } #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; schedstat_set(curr->statistics.exec_max, max(delta_exec, curr->statistics.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_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(struct cfs_rq *cfs_rq, struct sched_entity *se) { u64 wait_start, prev_wait_start; if (!schedstat_enabled()) return; wait_start = rq_clock(rq_of(cfs_rq)); prev_wait_start = schedstat_val(se->statistics.wait_start); if (entity_is_task(se) && task_on_rq_migrating(task_of(se)) && likely(wait_start > prev_wait_start)) wait_start -= prev_wait_start; __schedstat_set(se->statistics.wait_start, wait_start); } static inline void update_stats_wait_end(struct cfs_rq *cfs_rq, struct sched_entity *se) { struct task_struct *p; u64 delta; if (!schedstat_enabled()) return; delta = rq_clock(rq_of(cfs_rq)) - schedstat_val(se->statistics.wait_start); if (entity_is_task(se)) { p = task_of(se); if (task_on_rq_migrating(p)) { /* * Preserve migrating task's wait time so wait_start * time stamp can be adjusted to accumulate wait time * prior to migration. */ __schedstat_set(se->statistics.wait_start, delta); return; } trace_sched_stat_wait(p, delta); } __schedstat_set(se->statistics.wait_max, max(schedstat_val(se->statistics.wait_max), delta)); __schedstat_inc(se->statistics.wait_count); __schedstat_add(se->statistics.wait_sum, delta); __schedstat_set(se->statistics.wait_start, 0); } static inline void update_stats_enqueue_sleeper(struct cfs_rq *cfs_rq, struct sched_entity *se) { struct task_struct *tsk = NULL; u64 sleep_start, block_start; if (!schedstat_enabled()) return; sleep_start = schedstat_val(se->statistics.sleep_start); block_start = schedstat_val(se->statistics.block_start); if (entity_is_task(se)) tsk = task_of(se); if (sleep_start) { u64 delta = rq_clock(rq_of(cfs_rq)) - sleep_start; if ((s64)delta < 0) delta = 0; if (unlikely(delta > schedstat_val(se->statistics.sleep_max))) __schedstat_set(se->statistics.sleep_max, delta); __schedstat_set(se->statistics.sleep_start, 0); __schedstat_add(se->statistics.sum_sleep_runtime, delta); if (tsk) { account_scheduler_latency(tsk, delta >> 10, 1); trace_sched_stat_sleep(tsk, delta); } } if (block_start) { u64 delta = rq_clock(rq_of(cfs_rq)) - block_start; if ((s64)delta < 0) delta = 0; if (unlikely(delta > schedstat_val(se->statistics.block_max))) __schedstat_set(se->statistics.block_max, delta); __schedstat_set(se->statistics.block_start, 0); __schedstat_add(se->statistics.sum_sleep_runtime, delta); if (tsk) { if (tsk->in_iowait) { __schedstat_add(se->statistics.iowait_sum, delta); __schedstat_inc(se->statistics.iowait_count); trace_sched_stat_iowait(tsk, delta); } trace_sched_stat_blocked(tsk, delta); /* * Blocking time is in units of nanosecs, so shift by * 20 to get a milliseconds-range estimation of the * amount of time that the task spent sleeping: */ if (unlikely(prof_on == SLEEP_PROFILING)) { profile_hits(SLEEP_PROFILING, (void *)get_wchan(tsk), delta >> 20); } account_scheduler_latency(tsk, delta >> 10, 0); } } } /* * Task is being enqueued - update stats: */ static inline void update_stats_enqueue(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(cfs_rq, se); if (flags & ENQUEUE_WAKEUP) update_stats_enqueue_sleeper(cfs_rq, se); } static inline void update_stats_dequeue(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(cfs_rq, se); if ((flags & DEQUEUE_SLEEP) && entity_is_task(se)) { struct task_struct *tsk = task_of(se); if (tsk->state & TASK_INTERRUPTIBLE) __schedstat_set(se->statistics.sleep_start, rq_clock(rq_of(cfs_rq))); if (tsk->state & TASK_UNINTERRUPTIBLE) __schedstat_set(se->statistics.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: */ #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; struct numa_group { atomic_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_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_cpu; unsigned long faults[0]; }; 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 sanitys 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; /* Scale the maximum scan period with the amount of shared memory. */ if (p->numa_group) { struct numa_group *ng = p->numa_group; unsigned long shared = group_faults_shared(ng); unsigned long private = group_faults_priv(ng); period *= atomic_read(&ng->refcount); period *= shared + 1; period /= private + shared + 1; } return max(smin, period); } static unsigned int task_scan_max(struct task_struct *p) { unsigned long smin = task_scan_min(p); unsigned long smax; /* 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. */ if (p->numa_group) { struct numa_group *ng = p->numa_group; unsigned long shared = group_faults_shared(ng); unsigned long private = group_faults_priv(ng); unsigned long period = smax; period *= atomic_read(&ng->refcount); period *= shared + 1; period /= private + shared + 1; smax = max(smax, period); } return max(smin, smax); } 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_work.next = &p->numa_work; p->numa_faults = NULL; p->numa_group = NULL; p->last_task_numa_placement = 0; p->last_sum_exec_runtime = 0; /* New address space, reset the preferred nid */ if (!(clone_flags & CLONE_VM)) { p->numa_preferred_nid = -1; 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; } } static void account_numa_enqueue(struct rq *rq, struct task_struct *p) { rq->nr_numa_running += (p->numa_preferred_nid != -1); 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 != -1); 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) { return p->numa_group ? p->numa_group->gid : 0; } /* * 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) { if (!p->numa_group) return 0; return p->numa_group->faults[task_faults_idx(NUMA_MEM, nid, 0)] + p->numa_group->faults[task_faults_idx(NUMA_MEM, nid, 1)]; } static inline unsigned long group_faults_cpu(struct numa_group *group, int nid) { return group->faults_cpu[task_faults_idx(NUMA_MEM, nid, 0)] + group->faults_cpu[task_faults_idx(NUMA_MEM, 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 maxdist, bool task) { unsigned long score = 0; int node; /* * 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; /* * 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 == sched_max_numa_distance || 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 >= maxdist) 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 *= (sched_max_numa_distance - dist); faults /= (sched_max_numa_distance - 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) { unsigned long faults, total_faults; if (!p->numa_group) return 0; total_faults = p->numa_group->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; } bool should_numa_migrate_memory(struct task_struct *p, struct page * page, int src_nid, int dst_cpu) { struct numa_group *ng = p->numa_group; int dst_nid = cpu_to_node(dst_cpu); int last_cpupid, this_cpupid; this_cpupid = cpu_pid_to_cpupid(dst_cpu, current->pid); last_cpupid = page_cpupid_xchg_last(page, this_cpupid); /* * 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 == -1 || 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; } static unsigned long weighted_cpuload(struct rq *rq); static unsigned long source_load(int cpu, int type); static unsigned long target_load(int cpu, int type); static unsigned long capacity_of(int cpu); /* Cached statistics for all CPUs within a node */ struct numa_stats { unsigned long load; /* Total compute capacity of CPUs on a node */ unsigned long compute_capacity; unsigned int nr_running; }; /* * XXX borrowed from update_sg_lb_stats */ static void update_numa_stats(struct numa_stats *ns, int nid) { int smt, cpu, cpus = 0; unsigned long capacity; memset(ns, 0, sizeof(*ns)); for_each_cpu(cpu, cpumask_of_node(nid)) { struct rq *rq = cpu_rq(cpu); ns->nr_running += rq->nr_running; ns->load += weighted_cpuload(rq); ns->compute_capacity += capacity_of(cpu); cpus++; } /* * If we raced with hotplug and there are no CPUs left in our mask * the @ns structure is NULL'ed and task_numa_compare() will * not find this node attractive. * * We'll detect a huge imbalance and bail there. */ if (!cpus) return; /* smt := ceil(cpus / capacity), assumes: 1 < smt_power < 2 */ smt = DIV_ROUND_UP(SCHED_CAPACITY_SCALE * cpus, ns->compute_capacity); capacity = cpus / smt; /* cores */ capacity = min_t(unsigned, capacity, DIV_ROUND_CLOSEST(ns->compute_capacity, SCHED_CAPACITY_SCALE)); } struct task_numa_env { struct task_struct *p; int src_cpu, src_nid; int dst_cpu, dst_nid; struct numa_stats src_stats, dst_stats; int imbalance_pct; int dist; struct task_struct *best_task; long best_imp; int best_cpu; }; static void task_numa_assign(struct task_numa_env *env, struct task_struct *p, long imp) { struct rq *rq = cpu_rq(env->dst_cpu); /* Bail out if run-queue part of active NUMA balance. */ if (xchg(&rq->numa_migrate_on, 1)) return; /* * Clear previous best_cpu/rq numa-migrate flag, since task now * found a better CPU to move/swap. */ if (env->best_cpu != -1) { 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 void task_numa_compare(struct task_numa_env *env, long taskimp, long groupimp, bool maymove) { struct rq *dst_rq = cpu_rq(env->dst_cpu); struct task_struct *cur; long src_load, dst_load; long load; long imp = env->p->numa_group ? groupimp : taskimp; long moveimp = imp; int dist = env->dist; if (READ_ONCE(dst_rq->numa_migrate_on)) return; rcu_read_lock(); cur = task_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) goto unlock; if (!cur) { if (maymove && moveimp >= env->best_imp) goto assign; else 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. */ /* Skip this swap candidate if cannot move to the source cpu */ if (!cpumask_test_cpu(env->src_cpu, &cur->cpus_allowed)) goto unlock; /* * If dst and source tasks are in the same NUMA group, or not * in any group then look only at task weights. */ if (cur->numa_group == env->p->numa_group) { 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->numa_group) 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->numa_group && env->p->numa_group) 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); } if (maymove && moveimp > imp && moveimp > env->best_imp) { imp = moveimp; cur = NULL; 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: /* * One idle CPU per node is evaluated for a task numa move. * Call select_idle_sibling to maybe find a better one. */ if (!cur) { /* * select_idle_siblings() uses an per-CPU cpumask that * can be used from IRQ context. */ local_irq_disable(); env->dst_cpu = select_idle_sibling(env->p, env->src_cpu, env->dst_cpu); local_irq_enable(); } task_numa_assign(env, cur, imp); unlock: rcu_read_unlock(); } static void task_numa_find_cpu(struct task_numa_env *env, long taskimp, long groupimp) { long src_load, dst_load, load; bool maymove = false; int cpu; load = task_h_load(env->p); dst_load = env->dst_stats.load + load; src_load = env->src_stats.load - load; /* * If the improvement from just moving env->p direction is better * than swapping tasks around, check if a move is possible. */ 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_allowed)) continue; env->dst_cpu = cpu; task_numa_compare(env, taskimp, groupimp, maymove); } } 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, }; struct sched_domain *sd; struct rq *best_rq; unsigned long taskweight, groupweight; int nid, ret, dist; long taskimp, groupimp; /* * 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; 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.src_stats, env.src_nid); taskimp = task_weight(p, env.dst_nid, dist) - taskweight; groupimp = group_weight(p, env.dst_nid, dist) - groupweight; update_numa_stats(&env.dst_stats, env.dst_nid); /* 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. */ if (env.best_cpu == -1 || (p->numa_group && p->numa_group->active_nodes > 1)) { for_each_online_node(nid) { 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.dst_stats, env.dst_nid); 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 (p->numa_group) { 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) 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, 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, task_cpu(env.best_task)); 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 == -1 || !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 on 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_online_node(nid) { faults = group_faults_cpu(numa_group, nid); if (faults > max_faults) max_faults = faults; } for_each_online_node(nid) { 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 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; } 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_online_node(node) { 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_online_map; 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 = -1; unsigned long max_faults = 0; unsigned long fault_types[2] = { 0, 0 }; unsigned long total_faults; u64 runtime, period; spinlock_t *group_lock = NULL; /* * 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 */ if (p->numa_group) { group_lock = &p->numa_group->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 (p->numa_group) { /* * 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. */ p->numa_group->faults[mem_idx] += diff; p->numa_group->faults_cpu[mem_idx] += f_diff; p->numa_group->total_faults += diff; group_faults += p->numa_group->faults[mem_idx]; } } if (!p->numa_group) { if (faults > max_faults) { max_faults = faults; max_nid = nid; } } else if (group_faults > max_faults) { max_faults = group_faults; max_nid = nid; } } if (p->numa_group) { numa_group_count_active_nodes(p->numa_group); 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 atomic_inc_not_zero(&grp->refcount); } static inline void put_numa_group(struct numa_group *grp) { if (atomic_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(!p->numa_group)) { unsigned int size = sizeof(struct numa_group) + 4*nr_node_ids*sizeof(unsigned long); grp = kzalloc(size, GFP_KERNEL | __GFP_NOWARN); if (!grp) return; atomic_set(&grp->refcount, 1); grp->active_nodes = 1; grp->max_faults_cpu = 0; spin_lock_init(&grp->lock); grp->gid = p->pid; /* Second half of the array tracks nids where faults happen */ grp->faults_cpu = grp->faults + NR_NUMA_HINT_FAULT_TYPES * nr_node_ids; 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 = p->numa_group; 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; BUG_ON(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; } void task_numa_free(struct task_struct *p) { struct numa_group *grp = p->numa_group; void *numa_faults = p->numa_faults; unsigned long flags; int i; 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); } p->numa_faults = NULL; kfree(numa_faults); } /* * 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; /* 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 = p->numa_group; 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 task to preferred node migration periodically, in case it * 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; } /* * The expensive part of numa migration is done from task_work context. * Triggered from task_tick_numa(). */ 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; SCHED_WARN_ON(p != container_of(work, struct task_struct, numa_work)); work->next = work; /* protect against double add */ /* * 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 (cmpxchg(&mm->numa_next_scan, migrate, next_scan) != migrate) return; /* * Delay this task enough that another task of this mm will likely win * the next time around. */ p->node_stamp += 2 * TICK_NSEC; start = mm->numa_scan_offset; 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 (!down_read_trylock(&mm->mmap_sem)) return; vma = find_vma(mm, start); if (!vma) { reset_ptenuma_scan(p); start = 0; vma = mm->mmap; } for (; vma; vma = vma->vm_next) { if (!vma_migratable(vma) || !vma_policy_mof(vma) || is_vm_hugetlb_page(vma) || (vma->vm_flags & VM_MIXEDMAP)) { 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))) continue; /* * Skip inaccessible VMAs to avoid any confusion between * PROT_NONE and NUMA hinting ptes */ if (!(vma->vm_flags & (VM_READ | VM_EXEC | VM_WRITE))) 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); } 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); up_read(&mm->mmap_sem); /* * 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; } } /* * Drive the periodic memory faults.. */ 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) || 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)) { init_task_work(work, task_numa_work); /* TODO: move this into sched_fork() */ task_work_add(curr, work, true); } } } 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 != -1 && 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); if (!parent_entity(se)) update_load_add(&rq_of(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++; } static void account_entity_dequeue(struct cfs_rq *cfs_rq, struct sched_entity *se) { update_load_sub(&cfs_rq->load, se->load.weight); if (!parent_entity(se)) update_load_sub(&rq_of(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--; } /* * 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) #ifdef CONFIG_SMP static inline void enqueue_runnable_load_avg(struct cfs_rq *cfs_rq, struct sched_entity *se) { cfs_rq->runnable_weight += se->runnable_weight; cfs_rq->avg.runnable_load_avg += se->avg.runnable_load_avg; cfs_rq->avg.runnable_load_sum += se_runnable(se) * se->avg.runnable_load_sum; } static inline void dequeue_runnable_load_avg(struct cfs_rq *cfs_rq, struct sched_entity *se) { cfs_rq->runnable_weight -= se->runnable_weight; sub_positive(&cfs_rq->avg.runnable_load_avg, se->avg.runnable_load_avg); sub_positive(&cfs_rq->avg.runnable_load_sum, se_runnable(se) * se->avg.runnable_load_sum); } 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); } #else static inline void enqueue_runnable_load_avg(struct cfs_rq *cfs_rq, struct sched_entity *se) { } static inline void dequeue_runnable_load_avg(struct cfs_rq *cfs_rq, struct sched_entity *se) { } 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_entity(struct cfs_rq *cfs_rq, struct sched_entity *se, unsigned long weight, unsigned long runnable) { if (se->on_rq) { /* commit outstanding execution time */ if (cfs_rq->curr == se) update_curr(cfs_rq); account_entity_dequeue(cfs_rq, se); dequeue_runnable_load_avg(cfs_rq, se); } dequeue_load_avg(cfs_rq, se); se->runnable_weight = runnable; update_load_set(&se->load, weight); #ifdef CONFIG_SMP do { u32 divider = LOAD_AVG_MAX - 1024 + se->avg.period_contrib; se->avg.load_avg = div_u64(se_weight(se) * se->avg.load_sum, divider); se->avg.runnable_load_avg = div_u64(se_runnable(se) * se->avg.runnable_load_sum, divider); } while (0); #endif enqueue_load_avg(cfs_rq, se); if (se->on_rq) { account_entity_enqueue(cfs_rq, se); enqueue_runnable_load_avg(cfs_rq, se); } } 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, weight); load->inv_weight = sched_prio_to_wmult[prio]; } #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); } /* * This calculates the effective runnable weight for a group entity based on * the group entity weight calculated above. * * Because of the above approximation (2), our group entity weight is * an load_avg based ratio (3). This means that it includes blocked load and * does not represent the runnable weight. * * Approximate the group entity's runnable weight per ratio from the group * runqueue: * * grq->avg.runnable_load_avg * ge->runnable_weight = ge->load.weight * -------------------------- (7) * grq->avg.load_avg * * However, analogous to above, since the avg numbers are slow, this leads to * transients in the from-idle case. Instead we use: * * ge->runnable_weight = ge->load.weight * * * max(grq->avg.runnable_load_avg, grq->runnable_weight) * ----------------------------------------------------- (8) * max(grq->avg.load_avg, grq->load.weight) * * Where these max() serve both to use the 'instant' values to fix the slow * from-idle and avoid the /0 on to-idle, similar to (6). */ static long calc_group_runnable(struct cfs_rq *cfs_rq, long shares) { long runnable, load_avg; load_avg = max(cfs_rq->avg.load_avg, scale_load_down(cfs_rq->load.weight)); runnable = max(cfs_rq->avg.runnable_load_avg, scale_load_down(cfs_rq->runnable_weight)); runnable *= shares; if (load_avg) runnable /= load_avg; return clamp_t(long, runnable, MIN_SHARES, shares); } #endif /* CONFIG_SMP */ static inline int throttled_hierarchy(struct cfs_rq *cfs_rq); /* * 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, runnable; if (!gcfs_rq) return; if (throttled_hierarchy(gcfs_rq)) return; #ifndef CONFIG_SMP runnable = shares = READ_ONCE(gcfs_rq->tg->shares); if (likely(se->load.weight == shares)) return; #else shares = calc_group_shares(gcfs_rq); runnable = calc_group_runnable(gcfs_rq, shares); #endif reweight_entity(cfs_rq_of(se), se, shares, runnable); } #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 || (flags & SCHED_CPUFREQ_MIGRATION)) { /* * 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(). */ cpufreq_update_util(rq, flags); } } #ifdef CONFIG_SMP #ifdef CONFIG_FAIR_GROUP_SCHED /** * update_tg_load_avg - update the tg's load avg * @cfs_rq: the cfs_rq whose avg changed * @force: update regardless of how small the difference * * 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, int force) { long delta = cfs_rq->avg.load_avg - cfs_rq->tg_load_avg_contrib; /* * No need to update load_avg for root_task_group as it is not used. */ if (cfs_rq->tg == &root_task_group) return; if (force || 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; } } /* * 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; #ifndef CONFIG_64BIT { u64 p_last_update_time_copy; u64 n_last_update_time_copy; do { p_last_update_time_copy = prev->load_last_update_time_copy; n_last_update_time_copy = next->load_last_update_time_copy; smp_rmb(); p_last_update_time = prev->avg.last_update_time; n_last_update_time = next->avg.last_update_time; } while (p_last_update_time != p_last_update_time_copy || n_last_update_time != n_last_update_time_copy); } #else p_last_update_time = prev->avg.last_update_time; n_last_update_time = next->avg.last_update_time; #endif __update_load_avg_blocked_se(p_last_update_time, cpu_of(rq_of(prev)), 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() is trivial and simply copies the running * sum over (but still wrong, because the group entity and group rq do not have * their PELT windows aligned). * * However, update_tg_cfs_runnable() 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 = gcfs_rq->avg.util_avg - se->avg.util_avg; /* Nothing to update */ if (!delta) return; /* * The relation between sum and avg is: * * LOAD_AVG_MAX - 1024 + sa->period_contrib * * however, the PELT windows are not aligned between grq and gse. */ /* Set new sched_entity's utilization */ se->avg.util_avg = gcfs_rq->avg.util_avg; se->avg.util_sum = se->avg.util_avg * LOAD_AVG_MAX; /* Update parent cfs_rq utilization */ add_positive(&cfs_rq->avg.util_avg, delta); cfs_rq->avg.util_sum = cfs_rq->avg.util_avg * LOAD_AVG_MAX; } static inline void update_tg_cfs_runnable(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 runnable_load_avg, load_avg; u64 runnable_load_sum, load_sum = 0; s64 delta_sum; if (!runnable_sum) return; gcfs_rq->prop_runnable_sum = 0; 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(runnable_sum, (long)LOAD_AVG_MAX); } 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_s64(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 * As running sum is scale with CPU capacity wehreas the runnable sum * is not we rescale running_sum 1st */ running_sum = se->avg.util_sum / arch_scale_cpu_capacity(NULL, cpu_of(rq_of(cfs_rq))); runnable_sum = max(runnable_sum, running_sum); load_sum = (s64)se_weight(se) * runnable_sum; load_avg = div_s64(load_sum, LOAD_AVG_MAX); delta_sum = load_sum - (s64)se_weight(se) * se->avg.load_sum; delta_avg = load_avg - se->avg.load_avg; 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); runnable_load_sum = (s64)se_runnable(se) * runnable_sum; runnable_load_avg = div_s64(runnable_load_sum, LOAD_AVG_MAX); delta_sum = runnable_load_sum - se_weight(se) * se->avg.runnable_load_sum; delta_avg = runnable_load_avg - se->avg.runnable_load_avg; se->avg.runnable_load_sum = runnable_sum; se->avg.runnable_load_avg = runnable_load_avg; if (se->on_rq) { add_positive(&cfs_rq->avg.runnable_load_avg, delta_avg); add_positive(&cfs_rq->avg.runnable_load_sum, delta_sum); } } 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); 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, int force) {} 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 */ /** * update_cfs_rq_load_avg - update the cfs_rq's load/util averages * @now: current time, as per cfs_rq_clock_task() * @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, see * post_init_entity_util_avg(). * * cfs_rq->avg is used for task_h_load() and update_cfs_share() for example. * * Returns 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_sum = 0; struct sched_avg *sa = &cfs_rq->avg; int decayed = 0; if (cfs_rq->removed.nr) { unsigned long r; u32 divider = LOAD_AVG_MAX - 1024 + sa->period_contrib; 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_sum, removed_runnable_sum); 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); r = removed_util; sub_positive(&sa->util_avg, r); sub_positive(&sa->util_sum, r * divider); add_tg_cfs_propagate(cfs_rq, -(long)removed_runnable_sum); decayed = 1; } decayed |= __update_load_avg_cfs_rq(now, cpu_of(rq_of(cfs_rq)), cfs_rq); #ifndef CONFIG_64BIT smp_wmb(); cfs_rq->load_last_update_time_copy = sa->last_update_time; #endif if (decayed) cfs_rq_util_change(cfs_rq, 0); 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 * @flags: migration hints * * 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, int flags) { u32 divider = LOAD_AVG_MAX - 1024 + cfs_rq->avg.period_contrib; /* * 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.load_sum = divider; if (se_weight(se)) { se->avg.load_sum = div_u64(se->avg.load_avg * se->avg.load_sum, se_weight(se)); } se->avg.runnable_load_sum = se->avg.load_sum; enqueue_load_avg(cfs_rq, se); cfs_rq->avg.util_avg += se->avg.util_avg; cfs_rq->avg.util_sum += se->avg.util_sum; add_tg_cfs_propagate(cfs_rq, se->avg.load_sum); cfs_rq_util_change(cfs_rq, flags); } /** * 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); add_tg_cfs_propagate(cfs_rq, -se->avg.load_sum); cfs_rq_util_change(cfs_rq, 0); } /* * Optional action to be done while updating the load average */ #define UPDATE_TG 0x1 #define SKIP_AGE_LOAD 0x2 #define DO_ATTACH 0x4 /* 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_task(cfs_rq); struct rq *rq = rq_of(cfs_rq); int cpu = cpu_of(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, cpu, 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, SCHED_CPUFREQ_MIGRATION); update_tg_load_avg(cfs_rq, 0); } else if (decayed && (flags & UPDATE_TG)) update_tg_load_avg(cfs_rq, 0); } #ifndef CONFIG_64BIT static inline u64 cfs_rq_last_update_time(struct cfs_rq *cfs_rq) { u64 last_update_time_copy; u64 last_update_time; do { last_update_time_copy = cfs_rq->load_last_update_time_copy; smp_rmb(); last_update_time = cfs_rq->avg.last_update_time; } while (last_update_time != last_update_time_copy); return last_update_time; } #else static inline u64 cfs_rq_last_update_time(struct cfs_rq *cfs_rq) { return cfs_rq->avg.last_update_time; } #endif /* * Synchronize entity load avg of dequeued entity without locking * the previous rq. */ 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, cpu_of(rq_of(cfs_rq)), se); } /* * Task first catches up with cfs_rq, and then subtract * itself from the cfs_rq (task must be off the queue now). */ 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() -> * post_init_entity_util_avg() which will have added things to the * cfs_rq, so we can remove unconditionally. * * Similarly for groups, they will have passed through * post_init_entity_util_avg() before unregister_sched_fair_group() * calls this. */ 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_sum += se->avg.load_sum; /* == runnable_sum */ raw_spin_unlock_irqrestore(&cfs_rq->removed.lock, flags); } static inline unsigned long cfs_rq_runnable_load_avg(struct cfs_rq *cfs_rq) { return cfs_rq->avg.runnable_load_avg; } static inline unsigned long cfs_rq_load_avg(struct cfs_rq *cfs_rq) { return cfs_rq->avg.load_avg; } static int idle_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); } 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) | UTIL_AVG_UNCHANGED); WRITE_ONCE(cfs_rq->avg.util_est.enqueued, enqueued); } /* * 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 + maring < INT_MAX. */ static inline bool within_margin(int value, int margin) { return ((unsigned int)(value + margin - 1) < (2 * margin - 1)); } static void util_est_dequeue(struct cfs_rq *cfs_rq, struct task_struct *p, bool task_sleep) { long last_ewma_diff; struct util_est ue; if (!sched_feat(UTIL_EST)) return; /* Update root cfs_rq's estimated utilization */ ue.enqueued = cfs_rq->avg.util_est.enqueued; ue.enqueued -= min_t(unsigned int, ue.enqueued, (_task_util_est(p) | UTIL_AVG_UNCHANGED)); WRITE_ONCE(cfs_rq->avg.util_est.enqueued, ue.enqueued); /* * 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; /* * Skip update of task's estimated utilization when its EWMA is * already ~1% close to its last activation value. */ ue.enqueued = (task_util(p) | UTIL_AVG_UNCHANGED); last_ewma_diff = ue.enqueued - ue.ewma; if (within_margin(last_ewma_diff, (SCHED_CAPACITY_SCALE / 100))) 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; WRITE_ONCE(p->se.avg.util_est, ue); } #else /* CONFIG_SMP */ #define UPDATE_TG 0x0 #define SKIP_AGE_LOAD 0x0 #define DO_ATTACH 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, int flags) {} static inline void detach_entity_load_avg(struct cfs_rq *cfs_rq, struct sched_entity *se) {} static inline int idle_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, bool task_sleep) {} #endif /* CONFIG_SMP */ static void check_spread(struct cfs_rq *cfs_rq, struct sched_entity *se) { #ifdef CONFIG_SCHED_DEBUG s64 d = se->vruntime - cfs_rq->min_vruntime; if (d < 0) d = -d; if (d > 3*sysctl_sched_latency) schedstat_inc(cfs_rq->nr_spread_over); #endif } static void place_entity(struct cfs_rq *cfs_rq, struct sched_entity *se, int initial) { u64 vruntime = cfs_rq->min_vruntime; /* * The 'current' period is already promised to the current tasks, * however the extra weight of the new task will slow them down a * little, place the new task so that it fits in the slot that * stays open at the end. */ if (initial && sched_feat(START_DEBIT)) vruntime += sched_vslice(cfs_rq, se); /* sleeps up to a single latency don't count. */ if (!initial) { unsigned long thresh = sysctl_sched_latency; /* * Halve their sleep time's effect, to allow * for a gentler effect of sleepers: */ if (sched_feat(GENTLE_FAIR_SLEEPERS)) thresh >>= 1; vruntime -= thresh; } /* ensure we never gain time by being placed backwards. */ se->vruntime = max_vruntime(se->vruntime, vruntime); } static void check_enqueue_throttle(struct cfs_rq *cfs_rq); static inline void check_schedstat_required(void) { #ifdef CONFIG_SCHEDSTATS if (schedstat_enabled()) return; /* Force schedstat enabled if a dependent tracepoint is active */ if (trace_sched_stat_wait_enabled() || trace_sched_stat_sleep_enabled() || trace_sched_stat_iowait_enabled() || trace_sched_stat_blocked_enabled() || trace_sched_stat_runtime_enabled()) { printk_deferred_once("Scheduler tracepoints stat_sleep, stat_iowait, " "stat_blocked and stat_runtime require the " "kernel parameter schedstats=enable or " "kernel.sched_schedstats=1\n"); } #endif } /* * MIGRATION * * dequeue * update_curr() * update_min_vruntime() * vruntime -= min_vruntime * * enqueue * update_curr() * update_min_vruntime() * vruntime += min_vruntime * * this way the vruntime transition between RQs is done when both * min_vruntime are up-to-date. * * WAKEUP (remote) * * ->migrate_task_rq_fair() (p->state == TASK_WAKING) * vruntime -= min_vruntime * * enqueue * update_curr() * update_min_vruntime() * vruntime += min_vruntime * * this way we don't have the most up-to-date min_vruntime on the originating * CPU and an up-to-date min_vruntime on the destination CPU. */ static void enqueue_entity(struct cfs_rq *cfs_rq, struct sched_entity *se, int flags) { bool renorm = !(flags & ENQUEUE_WAKEUP) || (flags & ENQUEUE_MIGRATED); bool curr = cfs_rq->curr == se; /* * If we're the current task, we must renormalise before calling * update_curr(). */ if (renorm && curr) se->vruntime += cfs_rq->min_vruntime; update_curr(cfs_rq); /* * Otherwise, renormalise after, such that we're placed at the current * moment in time, instead of some random moment in the past. Being * placed in the past could significantly boost this task to the * fairness detriment of existing tasks. */ if (renorm && !curr) se->vruntime += cfs_rq->min_vruntime; /* * When enqueuing a sched_entity, we must: * - Update loads to have both entity and cfs_rq synced with now. * - Add its load to cfs_rq->runnable_avg * - 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); update_cfs_group(se); enqueue_runnable_load_avg(cfs_rq, se); account_entity_enqueue(cfs_rq, se); if (flags & ENQUEUE_WAKEUP) place_entity(cfs_rq, se, 0); check_schedstat_required(); update_stats_enqueue(cfs_rq, se, flags); check_spread(cfs_rq, se); if (!curr) __enqueue_entity(cfs_rq, se); se->on_rq = 1; if (cfs_rq->nr_running == 1) { list_add_leaf_cfs_rq(cfs_rq); check_enqueue_throttle(cfs_rq); } } static void __clear_buddies_last(struct sched_entity *se) { for_each_sched_entity(se) { struct cfs_rq *cfs_rq = cfs_rq_of(se); if (cfs_rq->last != se) break; cfs_rq->last = NULL; } } 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_skip(struct sched_entity *se) { for_each_sched_entity(se) { struct cfs_rq *cfs_rq = cfs_rq_of(se); if (cfs_rq->skip != se) break; cfs_rq->skip = NULL; } } static void clear_buddies(struct cfs_rq *cfs_rq, struct sched_entity *se) { if (cfs_rq->last == se) __clear_buddies_last(se); if (cfs_rq->next == se) __clear_buddies_next(se); if (cfs_rq->skip == se) __clear_buddies_skip(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) { /* * 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. * - Substract its load from the cfs_rq->runnable_avg. * - Substract 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, UPDATE_TG); dequeue_runnable_load_avg(cfs_rq, se); update_stats_dequeue(cfs_rq, se, flags); clear_buddies(cfs_rq, se); if (se != cfs_rq->curr) __dequeue_entity(cfs_rq, se); se->on_rq = 0; account_entity_dequeue(cfs_rq, se); /* * Normalize after update_curr(); which will also have moved * min_vruntime if @se is the one holding it back. But before doing * update_min_vruntime() again, which will discount @se's position and * can move min_vruntime forward still more. */ if (!(flags & DEQUEUE_SLEEP)) se->vruntime -= cfs_rq->min_vruntime; /* 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); } /* * Preempt the current task with a newly woken task if needed: */ static void check_preempt_tick(struct cfs_rq *cfs_rq, struct sched_entity *curr) { unsigned long ideal_runtime, delta_exec; struct sched_entity *se; s64 delta; ideal_runtime = sched_slice(cfs_rq, curr); delta_exec = curr->sum_exec_runtime - curr->prev_sum_exec_runtime; if (delta_exec > ideal_runtime) { resched_curr(rq_of(cfs_rq)); /* * The current task ran long enough, ensure it doesn't get * re-elected due to buddy favours. */ clear_buddies(cfs_rq, curr); return; } /* * Ensure that a task that missed wakeup preemption by a * narrow margin doesn't have to wait for a full slice. * This also mitigates buddy induced latencies under load. */ if (delta_exec < sysctl_sched_min_granularity) return; se = __pick_first_entity(cfs_rq); delta = curr->vruntime - se->vruntime; if (delta < 0) return; if (delta > ideal_runtime) resched_curr(rq_of(cfs_rq)); } static void set_next_entity(struct cfs_rq *cfs_rq, struct sched_entity *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(cfs_rq, se); __dequeue_entity(cfs_rq, se); update_load_avg(cfs_rq, se, UPDATE_TG); } 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)->load.weight >= 2*se->load.weight) { schedstat_set(se->statistics.slice_max, max((u64)schedstat_val(se->statistics.slice_max), se->sum_exec_runtime - se->prev_sum_exec_runtime)); } se->prev_sum_exec_runtime = se->sum_exec_runtime; } static int wakeup_preempt_entity(struct sched_entity *curr, struct sched_entity *se); /* * 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, struct sched_entity *curr) { struct sched_entity *left = __pick_first_entity(cfs_rq); struct sched_entity *se; /* * If curr is set we have to see if its left of the leftmost entity * still in the tree, provided there was anything in the tree at all. */ if (!left || (curr && entity_before(curr, left))) left = curr; se = left; /* ideally we run the leftmost entity */ /* * Avoid running the skip buddy, if running something else can * be done without getting too unfair. */ if (cfs_rq->skip == se) { struct sched_entity *second; if (se == curr) { second = __pick_first_entity(cfs_rq); } else { second = __pick_next_entity(se); if (!second || (curr && entity_before(curr, second))) second = curr; } if (second && wakeup_preempt_entity(second, left) < 1) se = second; } /* * Prefer last buddy, try to return the CPU to a preempted task. */ if (cfs_rq->last && wakeup_preempt_entity(cfs_rq->last, left) < 1) se = cfs_rq->last; /* * Someone really wants this to run. If it's not unfair, run it. */ if (cfs_rq->next && wakeup_preempt_entity(cfs_rq->next, left) < 1) se = cfs_rq->next; clear_buddies(cfs_rq, se); return se; } 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); check_spread(cfs_rq, prev); if (prev->on_rq) { update_stats_wait_start(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 if (cfs_rq->nr_running > 1) check_preempt_tick(cfs_rq, curr); } /************************************************** * CFS bandwidth control machinery */ #ifdef CONFIG_CFS_BANDWIDTH #ifdef HAVE_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 /* HAVE_JUMP_LABEL */ static bool cfs_bandwidth_used(void) { return true; } void cfs_bandwidth_usage_inc(void) {} void cfs_bandwidth_usage_dec(void) {} #endif /* HAVE_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 and update expiration time. * 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) { u64 now; if (cfs_b->quota == RUNTIME_INF) return; now = sched_clock_cpu(smp_processor_id()); cfs_b->runtime = cfs_b->quota; cfs_b->runtime_expires = now + ktime_to_ns(cfs_b->period); cfs_b->expires_seq++; } static inline struct cfs_bandwidth *tg_cfs_bandwidth(struct task_group *tg) { return &tg->cfs_bandwidth; } /* rq->task_clock normalized against any time this cfs_rq has spent throttled */ static inline u64 cfs_rq_clock_task(struct cfs_rq *cfs_rq) { if (unlikely(cfs_rq->throttle_count)) return cfs_rq->throttled_clock_task - cfs_rq->throttled_clock_task_time; return rq_clock_task(rq_of(cfs_rq)) - cfs_rq->throttled_clock_task_time; } /* returns 0 on failure to allocate runtime */ static int assign_cfs_rq_runtime(struct cfs_rq *cfs_rq) { struct task_group *tg = cfs_rq->tg; struct cfs_bandwidth *cfs_b = tg_cfs_bandwidth(tg); u64 amount = 0, min_amount, expires; int expires_seq; /* note: this is a positive sum as runtime_remaining <= 0 */ min_amount = sched_cfs_bandwidth_slice() - cfs_rq->runtime_remaining; raw_spin_lock(&cfs_b->lock); 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; } } expires_seq = cfs_b->expires_seq; expires = cfs_b->runtime_expires; raw_spin_unlock(&cfs_b->lock); cfs_rq->runtime_remaining += amount; /* * we may have advanced our local expiration to account for allowed * spread between our sched_clock and the one on which runtime was * issued. */ if (cfs_rq->expires_seq != expires_seq) { cfs_rq->expires_seq = expires_seq; cfs_rq->runtime_expires = expires; } return cfs_rq->runtime_remaining > 0; } /* * Note: This depends on the synchronization provided by sched_clock and the * fact that rq->clock snapshots this value. */ static void expire_cfs_rq_runtime(struct cfs_rq *cfs_rq) { struct cfs_bandwidth *cfs_b = tg_cfs_bandwidth(cfs_rq->tg); /* if the deadline is ahead of our clock, nothing to do */ if (likely((s64)(rq_clock(rq_of(cfs_rq)) - cfs_rq->runtime_expires) < 0)) return; if (cfs_rq->runtime_remaining < 0) return; /* * If the local deadline has passed we have to consider the * possibility that our sched_clock is 'fast' and the global deadline * has not truly expired. * * Fortunately we can check determine whether this the case by checking * whether the global deadline(cfs_b->expires_seq) has advanced. */ if (cfs_rq->expires_seq == cfs_b->expires_seq) { /* extend local deadline, drift is bounded above by 2 ticks */ cfs_rq->runtime_expires += TICK_NSEC; } else { /* global deadline is ahead, expiration has passed */ cfs_rq->runtime_remaining = 0; } } 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; expire_cfs_rq_runtime(cfs_rq); if (likely(cfs_rq->runtime_remaining > 0)) 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) { /* adjust cfs_rq_clock_task() */ cfs_rq->throttled_clock_task_time += rq_clock_task(rq) - cfs_rq->throttled_clock_task; } 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_task = rq_clock_task(rq); cfs_rq->throttle_count++; return 0; } static void 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, dequeue = 1; bool empty; 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; for_each_sched_entity(se) { struct cfs_rq *qcfs_rq = cfs_rq_of(se); /* throttled entity or throttle-on-deactivate */ if (!se->on_rq) break; if (dequeue) dequeue_entity(qcfs_rq, se, DEQUEUE_SLEEP); qcfs_rq->h_nr_running -= task_delta; if (qcfs_rq->load.weight) dequeue = 0; } if (!se) sub_nr_running(rq, task_delta); cfs_rq->throttled = 1; cfs_rq->throttled_clock = rq_clock(rq); raw_spin_lock(&cfs_b->lock); empty = list_empty(&cfs_b->throttled_cfs_rq); /* * Add to the _head_ of the list, so that an already-started * distribute_cfs_runtime will not see us. If disribute_cfs_runtime is * not running add to the tail so that later runqueues don't get starved. */ if (cfs_b->distribute_running) list_add_rcu(&cfs_rq->throttled_list, &cfs_b->throttled_cfs_rq); else list_add_tail_rcu(&cfs_rq->throttled_list, &cfs_b->throttled_cfs_rq); /* * If we're the first throttled task, make sure the bandwidth * timer is running. */ if (empty) start_cfs_bandwidth(cfs_b); raw_spin_unlock(&cfs_b->lock); } 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; int enqueue = 1; long task_delta; se = cfs_rq->tg->se[cpu_of(rq)]; cfs_rq->throttled = 0; update_rq_clock(rq); raw_spin_lock(&cfs_b->lock); cfs_b->throttled_time += rq_clock(rq) - cfs_rq->throttled_clock; 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) return; task_delta = cfs_rq->h_nr_running; for_each_sched_entity(se) { if (se->on_rq) enqueue = 0; cfs_rq = cfs_rq_of(se); if (enqueue) enqueue_entity(cfs_rq, se, ENQUEUE_WAKEUP); cfs_rq->h_nr_running += task_delta; if (cfs_rq_throttled(cfs_rq)) break; } if (!se) add_nr_running(rq, task_delta); /* Determine whether we need to wake up potentially idle CPU: */ if (rq->curr == rq->idle && rq->cfs.nr_running) resched_curr(rq); } static u64 distribute_cfs_runtime(struct cfs_bandwidth *cfs_b, u64 remaining, u64 expires) { struct cfs_rq *cfs_rq; u64 runtime; u64 starting_runtime = remaining; rcu_read_lock(); list_for_each_entry_rcu(cfs_rq, &cfs_b->throttled_cfs_rq, throttled_list) { struct rq *rq = rq_of(cfs_rq); struct rq_flags rf; rq_lock(rq, &rf); if (!cfs_rq_throttled(cfs_rq)) goto next; runtime = -cfs_rq->runtime_remaining + 1; if (runtime > remaining) runtime = remaining; remaining -= runtime; cfs_rq->runtime_remaining += runtime; cfs_rq->runtime_expires = expires; /* we check whether we're throttled above */ if (cfs_rq->runtime_remaining > 0) unthrottle_cfs_rq(cfs_rq); next: rq_unlock(rq, &rf); if (!remaining) break; } rcu_read_unlock(); return starting_runtime - remaining; } /* * 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) { u64 runtime, runtime_expires; 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; /* * 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; __refill_cfs_bandwidth_runtime(cfs_b); 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; runtime_expires = cfs_b->runtime_expires; /* * This check is repeated as we are holding onto the new bandwidth while * we unthrottle. This can potentially race with an unthrottled group * trying to acquire new bandwidth from the global pool. This can result * in us over-using our runtime if it is all used during this loop, but * only by limited amounts in that extreme case. */ while (throttled && cfs_b->runtime > 0 && !cfs_b->distribute_running) { runtime = cfs_b->runtime; cfs_b->distribute_running = 1; raw_spin_unlock(&cfs_b->lock); /* we can't nest cfs_b->lock while distributing bandwidth */ runtime = distribute_cfs_runtime(cfs_b, runtime, runtime_expires); raw_spin_lock(&cfs_b->lock); cfs_b->distribute_running = 0; throttled = !list_empty(&cfs_b->throttled_cfs_rq); cfs_b->runtime -= min(runtime, cfs_b->runtime); } /* * 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; u64 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 < 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; 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_rq->runtime_expires == cfs_b->runtime_expires) { 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(); u64 expires; /* confirm we're still not at a refresh boundary */ raw_spin_lock(&cfs_b->lock); if (cfs_b->distribute_running) { raw_spin_unlock(&cfs_b->lock); return; } if (runtime_refresh_within(cfs_b, min_bandwidth_expiration)) { raw_spin_unlock(&cfs_b->lock); return; } if (cfs_b->quota != RUNTIME_INF && cfs_b->runtime > slice) runtime = cfs_b->runtime; expires = cfs_b->runtime_expires; if (runtime) cfs_b->distribute_running = 1; raw_spin_unlock(&cfs_b->lock); if (!runtime) return; runtime = distribute_cfs_runtime(cfs_b, runtime, expires); raw_spin_lock(&cfs_b->lock); if (expires == cfs_b->runtime_expires) cfs_b->runtime -= min(runtime, cfs_b->runtime); cfs_b->distribute_running = 0; raw_spin_unlock(&cfs_b->lock); } /* * 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 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_task = rq_clock_task(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; throttle_cfs_rq(cfs_rq); return true; } 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; } static enum hrtimer_restart sched_cfs_period_timer(struct hrtimer *timer) { struct cfs_bandwidth *cfs_b = container_of(timer, struct cfs_bandwidth, period_timer); int overrun; int idle = 0; raw_spin_lock(&cfs_b->lock); for (;;) { overrun = hrtimer_forward_now(timer, cfs_b->period); if (!overrun) break; idle = do_sched_cfs_period_timer(cfs_b, overrun); } if (idle) cfs_b->period_active = 0; raw_spin_unlock(&cfs_b->lock); return idle ? HRTIMER_NORESTART : HRTIMER_RESTART; } void init_cfs_bandwidth(struct cfs_bandwidth *cfs_b) { 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()); 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; hrtimer_init(&cfs_b->slack_timer, CLOCK_MONOTONIC, HRTIMER_MODE_REL); cfs_b->slack_timer.function = sched_cfs_slack_timer; cfs_b->distribute_running = 0; } static void init_cfs_rq_runtime(struct cfs_rq *cfs_rq) { cfs_rq->runtime_enabled = 0; INIT_LIST_HEAD(&cfs_rq->throttled_list); } void start_cfs_bandwidth(struct cfs_bandwidth *cfs_b) { u64 overrun; lockdep_assert_held(&cfs_b->lock); if (cfs_b->period_active) return; cfs_b->period_active = 1; overrun = hrtimer_forward_now(&cfs_b->period_timer, cfs_b->period); cfs_b->runtime_expires += (overrun + 1) * ktime_to_ns(cfs_b->period); cfs_b->expires_seq++; hrtimer_start_expires(&cfs_b->period_timer, HRTIMER_MODE_ABS_PINNED); } static void destroy_cfs_bandwidth(struct cfs_bandwidth *cfs_b) { /* 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); } /* * 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 calback */ static void __maybe_unused update_runtime_enabled(struct rq *rq) { struct task_group *tg; lockdep_assert_held(&rq->lock); 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_held(&rq->lock); 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(); } #else /* CONFIG_CFS_BANDWIDTH */ static inline u64 cfs_rq_clock_task(struct cfs_rq *cfs_rq) { return rq_clock_task(rq_of(cfs_rq)); } 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; } void init_cfs_bandwidth(struct cfs_bandwidth *cfs_b) {} #ifdef CONFIG_FAIR_GROUP_SCHED 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) {} #endif /* CONFIG_CFS_BANDWIDTH */ /************************************************** * 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; struct cfs_rq *cfs_rq = cfs_rq_of(se); SCHED_WARN_ON(task_rq(p) != rq); if (rq->cfs.h_nr_running > 1) { u64 slice = sched_slice(cfs_rq, se); u64 ran = se->sum_exec_runtime - se->prev_sum_exec_runtime; s64 delta = slice - ran; if (delta < 0) { if (rq->curr == 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(rq) || curr->sched_class != &fair_sched_class) return; if (cfs_rq_of(&curr->se)->nr_running < sched_nr_latency) 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 /* * 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; /* * 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); /* * end evaluation on encountering a throttled cfs_rq * * note: in the case of encountering a throttled cfs_rq we will * post the final h_nr_running increment below. */ if (cfs_rq_throttled(cfs_rq)) break; cfs_rq->h_nr_running++; flags = ENQUEUE_WAKEUP; } for_each_sched_entity(se) { cfs_rq = cfs_rq_of(se); cfs_rq->h_nr_running++; if (cfs_rq_throttled(cfs_rq)) break; update_load_avg(cfs_rq, se, UPDATE_TG); update_cfs_group(se); } if (!se) add_nr_running(rq, 1); 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; for_each_sched_entity(se) { cfs_rq = cfs_rq_of(se); dequeue_entity(cfs_rq, se, flags); /* * end evaluation on encountering a throttled cfs_rq * * note: in the case of encountering a throttled cfs_rq we will * post the final h_nr_running decrement below. */ if (cfs_rq_throttled(cfs_rq)) break; cfs_rq->h_nr_running--; /* 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); cfs_rq->h_nr_running--; if (cfs_rq_throttled(cfs_rq)) break; update_load_avg(cfs_rq, se, UPDATE_TG); update_cfs_group(se); } if (!se) sub_nr_running(rq, 1); util_est_dequeue(&rq->cfs, p, task_sleep); hrtick_update(rq); } #ifdef CONFIG_SMP /* Working cpumask for: load_balance, load_balance_newidle. */ DEFINE_PER_CPU(cpumask_var_t, load_balance_mask); DEFINE_PER_CPU(cpumask_var_t, select_idle_mask); #ifdef CONFIG_NO_HZ_COMMON /* * per rq 'load' arrray crap; XXX kill this. */ /* * The exact cpuload calculated at every tick would be: * * load' = (1 - 1/2^i) * load + (1/2^i) * cur_load * * If a CPU misses updates for n ticks (as it was idle) and update gets * called on the n+1-th tick when CPU may be busy, then we have: * * load_n = (1 - 1/2^i)^n * load_0 * load_n+1 = (1 - 1/2^i) * load_n + (1/2^i) * cur_load * * decay_load_missed() below does efficient calculation of * * load' = (1 - 1/2^i)^n * load * * Because x^(n+m) := x^n * x^m we can decompose any x^n in power-of-2 factors. * This allows us to precompute the above in said factors, thereby allowing the * reduction of an arbitrary n in O(log_2 n) steps. (See also * fixed_power_int()) * * The calculation is approximated on a 128 point scale. */ #define DEGRADE_SHIFT 7 static const u8 degrade_zero_ticks[CPU_LOAD_IDX_MAX] = {0, 8, 32, 64, 128}; static const u8 degrade_factor[CPU_LOAD_IDX_MAX][DEGRADE_SHIFT + 1] = { { 0, 0, 0, 0, 0, 0, 0, 0 }, { 64, 32, 8, 0, 0, 0, 0, 0 }, { 96, 72, 40, 12, 1, 0, 0, 0 }, { 112, 98, 75, 43, 15, 1, 0, 0 }, { 120, 112, 98, 76, 45, 16, 2, 0 } }; /* * Update cpu_load for any missed ticks, due to tickless idle. The backlog * would be when CPU is idle and so we just decay the old load without * adding any new load. */ static unsigned long decay_load_missed(unsigned long load, unsigned long missed_updates, int idx) { int j = 0; if (!missed_updates) return load; if (missed_updates >= degrade_zero_ticks[idx]) return 0; if (idx == 1) return load >> missed_updates; while (missed_updates) { if (missed_updates % 2) load = (load * degrade_factor[idx][j]) >> DEGRADE_SHIFT; missed_updates >>= 1; j++; } return load; } static struct { cpumask_var_t idle_cpus_mask; atomic_t nr_cpus; int has_blocked; /* Idle CPUS has blocked load */ 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 */ /** * __cpu_load_update - update the rq->cpu_load[] statistics * @this_rq: The rq to update statistics for * @this_load: The current load * @pending_updates: The number of missed updates * * Update rq->cpu_load[] statistics. This function is usually called every * scheduler tick (TICK_NSEC). * * This function computes a decaying average: * * load[i]' = (1 - 1/2^i) * load[i] + (1/2^i) * load * * Because of NOHZ it might not get called on every tick which gives need for * the @pending_updates argument. * * load[i]_n = (1 - 1/2^i) * load[i]_n-1 + (1/2^i) * load_n-1 * = A * load[i]_n-1 + B ; A := (1 - 1/2^i), B := (1/2^i) * load * = A * (A * load[i]_n-2 + B) + B * = A * (A * (A * load[i]_n-3 + B) + B) + B * = A^3 * load[i]_n-3 + (A^2 + A + 1) * B * = A^n * load[i]_0 + (A^(n-1) + A^(n-2) + ... + 1) * B * = A^n * load[i]_0 + ((1 - A^n) / (1 - A)) * B * = (1 - 1/2^i)^n * (load[i]_0 - load) + load * * In the above we've assumed load_n := load, which is true for NOHZ_FULL as * any change in load would have resulted in the tick being turned back on. * * For regular NOHZ, this reduces to: * * load[i]_n = (1 - 1/2^i)^n * load[i]_0 * * see decay_load_misses(). For NOHZ_FULL we get to subtract and add the extra * term. */ static void cpu_load_update(struct rq *this_rq, unsigned long this_load, unsigned long pending_updates) { unsigned long __maybe_unused tickless_load = this_rq->cpu_load[0]; int i, scale; this_rq->nr_load_updates++; /* Update our load: */ this_rq->cpu_load[0] = this_load; /* Fasttrack for idx 0 */ for (i = 1, scale = 2; i < CPU_LOAD_IDX_MAX; i++, scale += scale) { unsigned long old_load, new_load; /* scale is effectively 1 << i now, and >> i divides by scale */ old_load = this_rq->cpu_load[i]; #ifdef CONFIG_NO_HZ_COMMON old_load = decay_load_missed(old_load, pending_updates - 1, i); if (tickless_load) { old_load -= decay_load_missed(tickless_load, pending_updates - 1, i); /* * old_load can never be a negative value because a * decayed tickless_load cannot be greater than the * original tickless_load. */ old_load += tickless_load; } #endif new_load = this_load; /* * Round up the averaging division if load is increasing. This * prevents us from getting stuck on 9 if the load is 10, for * example. */ if (new_load > old_load) new_load += scale - 1; this_rq->cpu_load[i] = (old_load * (scale - 1) + new_load) >> i; } } /* Used instead of source_load when we know the type == 0 */ static unsigned long weighted_cpuload(struct rq *rq) { return cfs_rq_runnable_load_avg(&rq->cfs); } #ifdef CONFIG_NO_HZ_COMMON /* * There is no sane way to deal with nohz on smp when using jiffies because the * CPU doing the jiffies update might drift wrt the CPU doing the jiffy reading * causing off-by-one errors in observed deltas; {0,2} instead of {1,1}. * * Therefore we need to avoid the delta approach from the regular tick when * possible since that would seriously skew the load calculation. This is why we * use cpu_load_update_periodic() for CPUs out of nohz. However we'll rely on * jiffies deltas for updates happening while in nohz mode (idle ticks, idle * loop exit, nohz_idle_balance, nohz full exit...) * * This means we might still be one tick off for nohz periods. */ static void cpu_load_update_nohz(struct rq *this_rq, unsigned long curr_jiffies, unsigned long load) { unsigned long pending_updates; pending_updates = curr_jiffies - this_rq->last_load_update_tick; if (pending_updates) { this_rq->last_load_update_tick = curr_jiffies; /* * In the regular NOHZ case, we were idle, this means load 0. * In the NOHZ_FULL case, we were non-idle, we should consider * its weighted load. */ cpu_load_update(this_rq, load, pending_updates); } } /* * Called from nohz_idle_balance() to update the load ratings before doing the * idle balance. */ static void cpu_load_update_idle(struct rq *this_rq) { /* * bail if there's load or we're actually up-to-date. */ if (weighted_cpuload(this_rq)) return; cpu_load_update_nohz(this_rq, READ_ONCE(jiffies), 0); } /* * Record CPU load on nohz entry so we know the tickless load to account * on nohz exit. cpu_load[0] happens then to be updated more frequently * than other cpu_load[idx] but it should be fine as cpu_load readers * shouldn't rely into synchronized cpu_load[*] updates. */ void cpu_load_update_nohz_start(void) { struct rq *this_rq = this_rq(); /* * This is all lockless but should be fine. If weighted_cpuload changes * concurrently we'll exit nohz. And cpu_load write can race with * cpu_load_update_idle() but both updater would be writing the same. */ this_rq->cpu_load[0] = weighted_cpuload(this_rq); } /* * Account the tickless load in the end of a nohz frame. */ void cpu_load_update_nohz_stop(void) { unsigned long curr_jiffies = READ_ONCE(jiffies); struct rq *this_rq = this_rq(); unsigned long load; struct rq_flags rf; if (curr_jiffies == this_rq->last_load_update_tick) return; load = weighted_cpuload(this_rq); rq_lock(this_rq, &rf); update_rq_clock(this_rq); cpu_load_update_nohz(this_rq, curr_jiffies, load); rq_unlock(this_rq, &rf); } #else /* !CONFIG_NO_HZ_COMMON */ static inline void cpu_load_update_nohz(struct rq *this_rq, unsigned long curr_jiffies, unsigned long load) { } #endif /* CONFIG_NO_HZ_COMMON */ static void cpu_load_update_periodic(struct rq *this_rq, unsigned long load) { #ifdef CONFIG_NO_HZ_COMMON /* See the mess around cpu_load_update_nohz(). */ this_rq->last_load_update_tick = READ_ONCE(jiffies); #endif cpu_load_update(this_rq, load, 1); } /* * Called from scheduler_tick() */ void cpu_load_update_active(struct rq *this_rq) { unsigned long load = weighted_cpuload(this_rq); if (tick_nohz_tick_stopped()) cpu_load_update_nohz(this_rq, READ_ONCE(jiffies), load); else cpu_load_update_periodic(this_rq, load); } /* * Return a low guess at the load of a migration-source CPU weighted * according to the scheduling class and "nice" value. * * We want to under-estimate the load of migration sources, to * balance conservatively. */ static unsigned long source_load(int cpu, int type) { struct rq *rq = cpu_rq(cpu); unsigned long total = weighted_cpuload(rq); if (type == 0 || !sched_feat(LB_BIAS)) return total; return min(rq->cpu_load[type-1], total); } /* * Return a high guess at the load of a migration-target CPU weighted * according to the scheduling class and "nice" value. */ static unsigned long target_load(int cpu, int type) { struct rq *rq = cpu_rq(cpu); unsigned long total = weighted_cpuload(rq); if (type == 0 || !sched_feat(LB_BIAS)) return total; return max(rq->cpu_load[type-1], total); } static unsigned long capacity_of(int cpu) { return cpu_rq(cpu)->cpu_capacity; } static unsigned long capacity_orig_of(int cpu) { return cpu_rq(cpu)->cpu_capacity_orig; } static unsigned long cpu_avg_load_per_task(int cpu) { struct rq *rq = cpu_rq(cpu); unsigned long nr_running = READ_ONCE(rq->cfs.h_nr_running); unsigned long load_avg = weighted_cpuload(rq); if (nr_running) return load_avg / nr_running; return 0; } 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; 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 = target_load(this_cpu, sd->wake_idx); 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 = source_load(prev_cpu, sd->wake_idx); 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->se.statistics.nr_wakeups_affine_attempts); if (target == nr_cpumask_bits) return prev_cpu; schedstat_inc(sd->ttwu_move_affine); schedstat_inc(p->se.statistics.nr_wakeups_affine); return target; } static unsigned long cpu_util_wake(int cpu, struct task_struct *p); static unsigned long capacity_spare_wake(int cpu, struct task_struct *p) { return max_t(long, capacity_of(cpu) - cpu_util_wake(cpu, p), 0); } /* * 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, int sd_flag) { struct sched_group *idlest = NULL, *group = sd->groups; struct sched_group *most_spare_sg = NULL; unsigned long min_runnable_load = ULONG_MAX; unsigned long this_runnable_load = ULONG_MAX; unsigned long min_avg_load = ULONG_MAX, this_avg_load = ULONG_MAX; unsigned long most_spare = 0, this_spare = 0; int load_idx = sd->forkexec_idx; int imbalance_scale = 100 + (sd->imbalance_pct-100)/2; unsigned long imbalance = scale_load_down(NICE_0_LOAD) * (sd->imbalance_pct-100) / 100; if (sd_flag & SD_BALANCE_WAKE) load_idx = sd->wake_idx; do { unsigned long load, avg_load, runnable_load; unsigned long spare_cap, max_spare_cap; int local_group; int i; /* Skip over this group if it has no CPUs allowed */ if (!cpumask_intersects(sched_group_span(group), &p->cpus_allowed)) continue; local_group = cpumask_test_cpu(this_cpu, sched_group_span(group)); /* * Tally up the load of all CPUs in the group and find * the group containing the CPU with most spare capacity. */ avg_load = 0; runnable_load = 0; max_spare_cap = 0; for_each_cpu(i, sched_group_span(group)) { /* Bias balancing toward CPUs of our domain */ if (local_group) load = source_load(i, load_idx); else load = target_load(i, load_idx); runnable_load += load; avg_load += cfs_rq_load_avg(&cpu_rq(i)->cfs); spare_cap = capacity_spare_wake(i, p); if (spare_cap > max_spare_cap) max_spare_cap = spare_cap; } /* Adjust by relative CPU capacity of the group */ avg_load = (avg_load * SCHED_CAPACITY_SCALE) / group->sgc->capacity; runnable_load = (runnable_load * SCHED_CAPACITY_SCALE) / group->sgc->capacity; if (local_group) { this_runnable_load = runnable_load; this_avg_load = avg_load; this_spare = max_spare_cap; } else { if (min_runnable_load > (runnable_load + imbalance)) { /* * The runnable load is significantly smaller * so we can pick this new CPU: */ min_runnable_load = runnable_load; min_avg_load = avg_load; idlest = group; } else if ((runnable_load < (min_runnable_load + imbalance)) && (100*min_avg_load > imbalance_scale*avg_load)) { /* * The runnable loads are close so take the * blocked load into account through avg_load: */ min_avg_load = avg_load; idlest = group; } if (most_spare < max_spare_cap) { most_spare = max_spare_cap; most_spare_sg = group; } } } while (group = group->next, group != sd->groups); /* * The cross-over point between using spare capacity or least load * is too conservative for high utilization tasks on partially * utilized systems if we require spare_capacity > task_util(p), * so we allow for some task stuffing by using * spare_capacity > task_util(p)/2. * * Spare capacity can't be used for fork because the utilization has * not been set yet, we must first select a rq to compute the initial * utilization. */ if (sd_flag & SD_BALANCE_FORK) goto skip_spare; if (this_spare > task_util(p) / 2 && imbalance_scale*this_spare > 100*most_spare) return NULL; if (most_spare > task_util(p) / 2) return most_spare_sg; skip_spare: if (!idlest) return NULL; /* * 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 runnable load on the remote node and consider * staying local. */ if ((sd->flags & SD_NUMA) && min_runnable_load + imbalance >= this_runnable_load) return NULL; if (min_runnable_load > (this_runnable_load + imbalance)) return NULL; if ((this_runnable_load < (min_runnable_load + imbalance)) && (100*this_avg_load < imbalance_scale*min_avg_load)) return NULL; return idlest; } /* * 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_allowed) { if (available_idle_cpu(i)) { struct rq *rq = cpu_rq(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 = weighted_cpuload(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_allowed)) return prev_cpu; /* * We need task's util for capacity_spare_wake, 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, sd_flag); 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; } #ifdef CONFIG_SCHED_SMT DEFINE_STATIC_KEY_FALSE(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, bool def) { struct sched_domain_shared *sds; sds = rcu_dereference(per_cpu(sd_llc_shared, cpu)); if (sds) return READ_ONCE(sds->has_idle_cores); return def; } /* * 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, true)) 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, struct sched_domain *sd, int target) { struct cpumask *cpus = this_cpu_cpumask_var_ptr(select_idle_mask); int core, cpu; if (!static_branch_likely(&sched_smt_present)) return -1; if (!test_idle_cores(target, false)) return -1; cpumask_and(cpus, sched_domain_span(sd), &p->cpus_allowed); for_each_cpu_wrap(core, cpus, target) { bool idle = true; for_each_cpu(cpu, cpu_smt_mask(core)) { cpumask_clear_cpu(cpu, cpus); if (!available_idle_cpu(cpu)) idle = false; } if (idle) return core; } /* * Failed to find an idle core; stop looking for one. */ set_idle_cores(target, 0); return -1; } /* * Scan the local SMT mask for idle CPUs. */ static int select_idle_smt(struct task_struct *p, struct sched_domain *sd, int target) { int cpu; if (!static_branch_likely(&sched_smt_present)) return -1; for_each_cpu(cpu, cpu_smt_mask(target)) { if (!cpumask_test_cpu(cpu, &p->cpus_allowed)) continue; if (available_idle_cpu(cpu)) return cpu; } return -1; } #else /* CONFIG_SCHED_SMT */ static inline int select_idle_core(struct task_struct *p, struct sched_domain *sd, int target) { return -1; } static inline int select_idle_smt(struct task_struct *p, struct sched_domain *sd, 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, int target) { struct sched_domain *this_sd; u64 avg_cost, avg_idle; u64 time, cost; s64 delta; int cpu, nr = INT_MAX; this_sd = rcu_dereference(*this_cpu_ptr(&sd_llc)); if (!this_sd) return -1; /* * Due to large variance we need a large fuzz factor; hackbench in * particularly is sensitive here. */ avg_idle = this_rq()->avg_idle / 512; avg_cost = this_sd->avg_scan_cost + 1; if (sched_feat(SIS_AVG_CPU) && avg_idle < avg_cost) return -1; if (sched_feat(SIS_PROP)) { u64 span_avg = sd->span_weight * avg_idle; if (span_avg > 4*avg_cost) nr = div_u64(span_avg, avg_cost); else nr = 4; } time = local_clock(); for_each_cpu_wrap(cpu, sched_domain_span(sd), target) { if (!--nr) return -1; if (!cpumask_test_cpu(cpu, &p->cpus_allowed)) continue; if (available_idle_cpu(cpu)) break; } time = local_clock() - time; cost = this_sd->avg_scan_cost; delta = (s64)(time - cost) / 8; this_sd->avg_scan_cost += delta; return cpu; } /* * 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) { struct sched_domain *sd; int i, recent_used_cpu; if (available_idle_cpu(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)) return prev; /* Check a recently used CPU as a potential idle candidate: */ recent_used_cpu = p->recent_used_cpu; if (recent_used_cpu != prev && recent_used_cpu != target && cpus_share_cache(recent_used_cpu, target) && available_idle_cpu(recent_used_cpu) && cpumask_test_cpu(p->recent_used_cpu, &p->cpus_allowed)) { /* * Replace recent_used_cpu with prev as it is a potential * candidate for the next wake: */ p->recent_used_cpu = prev; return recent_used_cpu; } sd = rcu_dereference(per_cpu(sd_llc, target)); if (!sd) return target; i = select_idle_core(p, sd, target); if ((unsigned)i < nr_cpumask_bits) return i; i = select_idle_cpu(p, sd, target); if ((unsigned)i < nr_cpumask_bits) return i; i = select_idle_smt(p, sd, target); if ((unsigned)i < nr_cpumask_bits) return i; return target; } /** * Amount of capacity of a CPU that is (estimated to be) used by CFS tasks * @cpu: the CPU to get the utilization of * * The unit of the return value must be the one of capacity so we can compare * the utilization with the capacity of the CPU that is available for CFS task * (ie cpu_capacity). * * cfs_rq.avg.util_avg is the sum of running time of runnable tasks plus the * recent utilization of currently non-runnable tasks on a CPU. It represents * the amount of utilization of a CPU in the range [0..capacity_orig] where * capacity_orig is the cpu_capacity available at the highest frequency * (arch_scale_freq_capacity()). * The utilization of a CPU converges towards a sum equal to or less than the * current capacity (capacity_curr <= capacity_orig) of the CPU because it is * the running time on this CPU scaled by capacity_curr. * * The estimated utilization of a CPU is defined to be the maximum between its * cfs_rq.avg.util_avg and the sum of the estimated utilization of the tasks * currently RUNNABLE on that CPU. * This allows to properly represent the expected utilization of a CPU which * has just got a big task running since a long sleep period. At the same time * however it preserves the benefits of the "blocked utilization" in * describing the potential for other tasks waking up on the same CPU. * * Nevertheless, cfs_rq.avg.util_avg can be higher than capacity_curr or even * higher than capacity_orig because of unfortunate rounding in * cfs.avg.util_avg or just after migrating tasks and new task wakeups until * the average stabilizes with the new running time. We need to check that the * utilization stays within the range of [0..capacity_orig] and cap it if * necessary. Without utilization capping, a group could be seen as overloaded * (CPU0 utilization at 121% + CPU1 utilization at 80%) whereas CPU1 has 20% of * available capacity. We allow utilization to overshoot capacity_curr (but not * capacity_orig) as it useful for predicting the capacity required after task * migrations (scheduler-driven DVFS). * * Return: the (estimated) utilization for the specified CPU */ static inline unsigned long cpu_util(int cpu) { struct cfs_rq *cfs_rq; unsigned int util; cfs_rq = &cpu_rq(cpu)->cfs; util = READ_ONCE(cfs_rq->avg.util_avg); if (sched_feat(UTIL_EST)) util = max(util, READ_ONCE(cfs_rq->avg.util_est.enqueued)); return min_t(unsigned long, util, capacity_orig_of(cpu)); } /* * cpu_util_wake: Compute CPU utilization with any contributions from * the waking task p removed. */ static unsigned long cpu_util_wake(int cpu, struct task_struct *p) { struct cfs_rq *cfs_rq; unsigned int util; /* Task has no contribution or is new */ if (cpu != task_cpu(p) || !READ_ONCE(p->se.avg.last_update_time)) return cpu_util(cpu); cfs_rq = &cpu_rq(cpu)->cfs; util = READ_ONCE(cfs_rq->avg.util_avg); /* Discount task's blocked util from CPU's util */ util -= min_t(unsigned int, util, task_util(p)); /* * Covered cases: * * a) if *p is the only task sleeping on this CPU, then: * cpu_util (== task_util) > util_est (== 0) * and thus we return: * cpu_util_wake = (cpu_util - task_util) = 0 * * b) if other tasks are SLEEPING on this CPU, which is now exiting * IDLE, then: * cpu_util >= task_util * cpu_util > util_est (== 0) * and thus we discount *p's blocked utilization to return: * cpu_util_wake = (cpu_util - task_util) >= 0 * * c) if other tasks are RUNNABLE on that CPU and * util_est > cpu_util * then we use util_est since it returns a more restrictive * estimation of the spare capacity on that CPU, by just * considering the expected utilization of tasks already * runnable on that CPU. * * Cases a) and b) are covered by the above code, while case c) is * covered by the following code when estimated utilization is * enabled. */ if (sched_feat(UTIL_EST)) util = max(util, READ_ONCE(cfs_rq->avg.util_est.enqueued)); /* * Utilization (estimated) can exceed the CPU capacity, thus let's * clamp to the maximum CPU capacity to ensure consistency with * the cpu_util call. */ return min_t(unsigned long, util, capacity_orig_of(cpu)); } /* * Disable WAKE_AFFINE in the case where task @p doesn't fit in the * capacity of either the waking CPU @cpu or the previous CPU @prev_cpu. * * In that case WAKE_AFFINE doesn't make sense and we'll let * BALANCE_WAKE sort things out. */ static int wake_cap(struct task_struct *p, int cpu, int prev_cpu) { long min_cap, max_cap; min_cap = min(capacity_orig_of(prev_cpu), capacity_orig_of(cpu)); max_cap = cpu_rq(cpu)->rd->max_cpu_capacity; /* Minimum capacity is close to max, no need to abort wake_affine */ if (max_cap - min_cap < max_cap >> 3) return 0; /* Bring task utilization in sync with prev_cpu */ sync_entity_load_avg(&p->se); return min_cap * 1024 < task_util(p) * capacity_margin; } /* * select_task_rq_fair: Select target runqueue for the waking task in domains * that have the 'sd_flag' 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. * * preempt must be disabled. */ static int select_task_rq_fair(struct task_struct *p, int prev_cpu, int sd_flag, int wake_flags) { struct sched_domain *tmp, *sd = NULL; int cpu = smp_processor_id(); int new_cpu = prev_cpu; int want_affine = 0; int sync = (wake_flags & WF_SYNC) && !(current->flags & PF_EXITING); if (sd_flag & SD_BALANCE_WAKE) { record_wakee(p); want_affine = !wake_wide(p) && !wake_cap(p, cpu, prev_cpu) && cpumask_test_cpu(cpu, &p->cpus_allowed); } rcu_read_lock(); for_each_domain(cpu, tmp) { if (!(tmp->flags & SD_LOAD_BALANCE)) break; /* * 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; } 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 (sd_flag & SD_BALANCE_WAKE) { /* XXX always ? */ /* Fast path */ new_cpu = select_idle_sibling(p, prev_cpu, new_cpu); if (want_affine) current->recent_used_cpu = cpu; } rcu_read_unlock(); return new_cpu; } static void detach_entity_cfs_rq(struct sched_entity *se); /* * 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) { /* * As blocked tasks retain absolute vruntime the migration needs to * deal with this by subtracting the old and adding the new * min_vruntime -- the latter is done by enqueue_entity() when placing * the task on the new runqueue. */ if (p->state == TASK_WAKING) { struct sched_entity *se = &p->se; struct cfs_rq *cfs_rq = cfs_rq_of(se); u64 min_vruntime; #ifndef CONFIG_64BIT u64 min_vruntime_copy; do { min_vruntime_copy = cfs_rq->min_vruntime_copy; smp_rmb(); min_vruntime = cfs_rq->min_vruntime; } while (min_vruntime != min_vruntime_copy); #else min_vruntime = cfs_rq->min_vruntime; #endif se->vruntime -= min_vruntime; } if (p->on_rq == TASK_ON_RQ_MIGRATING) { /* * In case of TASK_ON_RQ_MIGRATING we in fact hold the 'old' * rq->lock and can modify state directly. */ lockdep_assert_held(&task_rq(p)->lock); detach_entity_cfs_rq(&p->se); } else { /* * 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. */ remove_entity_load_avg(&p->se); } /* Tell new CPU we are migrated */ p->se.avg.last_update_time = 0; /* We have migrated, no longer consider this task hot */ p->se.exec_start = 0; update_scan_period(p, new_cpu); } static void task_dead_fair(struct task_struct *p) { remove_entity_load_avg(&p->se); } #endif /* CONFIG_SMP */ static unsigned long wakeup_gran(struct sched_entity *se) { unsigned long gran = sysctl_sched_wakeup_granularity; /* * Since its curr running now, convert the gran from real-time * to virtual-time in his units. * * By using 'se' instead of 'curr' we penalize light tasks, so * they get preempted easier. That is, if 'se' < 'curr' then * the resulting gran will be larger, therefore penalizing the * lighter, if otoh 'se' > 'curr' then the resulting gran will * be smaller, again penalizing the lighter task. * * This is especially important for buddies when the leftmost * task is higher priority than the buddy. */ return calc_delta_fair(gran, se); } /* * Should 'se' preempt 'curr'. * * |s1 * |s2 * |s3 * g * |<--->|c * * w(c, s1) = -1 * w(c, s2) = 0 * w(c, s3) = 1 * */ static int wakeup_preempt_entity(struct sched_entity *curr, struct sched_entity *se) { s64 gran, vdiff = curr->vruntime - se->vruntime; if (vdiff <= 0) return -1; gran = wakeup_gran(se); if (vdiff > gran) return 1; return 0; } static void set_last_buddy(struct sched_entity *se) { if (entity_is_task(se) && unlikely(task_of(se)->policy == SCHED_IDLE)) return; for_each_sched_entity(se) { if (SCHED_WARN_ON(!se->on_rq)) return; cfs_rq_of(se)->last = se; } } static void set_next_buddy(struct sched_entity *se) { if (entity_is_task(se) && unlikely(task_of(se)->policy == SCHED_IDLE)) return; for_each_sched_entity(se) { if (SCHED_WARN_ON(!se->on_rq)) return; cfs_rq_of(se)->next = se; } } static void set_skip_buddy(struct sched_entity *se) { for_each_sched_entity(se) cfs_rq_of(se)->skip = se; } /* * Preempt the current task with a newly woken task if needed: */ static void check_preempt_wakeup(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 scale = cfs_rq->nr_running >= sched_nr_latency; int next_buddy_marked = 0; if (unlikely(se == pse)) return; /* * This is possible from callers such as attach_tasks(), in which we * unconditionally check_prempt_curr() 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) && scale && !(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(curr->policy == SCHED_IDLE) && likely(p->policy != SCHED_IDLE)) 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); update_curr(cfs_rq_of(se)); BUG_ON(!pse); if (wakeup_preempt_entity(se, pse) == 1) { /* * Bias pick_next to pick the sched entity that is * triggering this preemption. */ if (!next_buddy_marked) set_next_buddy(pse); goto preempt; } return; preempt: resched_curr(rq); /* * Only set the backward buddy when the current task is still * on the rq. This can happen when a wakeup gets interleaved * with schedule on the ->pre_schedule() or idle_balance() * point, either of which can * drop the rq lock. * * Also, during early boot the idle thread is in the fair class, * for obvious reasons its a bad idea to schedule back to it. */ if (unlikely(!se->on_rq || curr == rq->idle)) return; if (sched_feat(LAST_BUDDY) && scale && entity_is_task(se)) set_last_buddy(se); } static 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 (!cfs_rq->nr_running) goto idle; #ifdef CONFIG_FAIR_GROUP_SCHED if (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, curr); 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 put_prev_task(rq, prev); do { se = pick_next_entity(cfs_rq, NULL); 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(rq)) hrtick_start_fair(rq, p); return p; idle: new_tasks = idle_balance(rq, rf); /* * Because idle_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; return 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 * * The magic of dealing with the ->skip buddy is in pick_next_entity. */ 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); if (curr->policy != SCHED_BATCH) { 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); } set_skip_buddy(se); } static bool yield_to_task_fair(struct rq *rq, struct task_struct *p, bool preempt) { 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 }; #define LBF_ALL_PINNED 0x01 #define LBF_NEED_BREAK 0x02 #define LBF_DST_PINNED 0x04 #define LBF_SOME_PINNED 0x08 #define LBF_NOHZ_STATS 0x10 #define LBF_NOHZ_AGAIN 0x20 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; 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_held(&env->src_rq->lock); if (p->sched_class != &fair_sched_class) return 0; if (unlikely(p->policy == SCHED_IDLE)) 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 || &p->se == cfs_rq_of(&p->se)->last)) return 1; if (sysctl_sched_migration_cost == -1) 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_held(&env->src_rq->lock); /* * We do not migrate tasks that are: * 1) throttled_lb_pair, or * 2) cannot be migrated to this CPU due to cpus_allowed, 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; if (!cpumask_test_cpu(env->dst_cpu, &p->cpus_allowed)) { int cpu; schedstat_inc(p->se.statistics.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 or if we have * already computed one in current iteration. */ if (env->idle == CPU_NEWLY_IDLE || (env->flags & LBF_DST_PINNED)) 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_allowed)) { env->flags |= LBF_DST_PINNED; env->new_dst_cpu = cpu; break; } } return 0; } /* Record that we found atleast one task that could run on dst_cpu */ env->flags &= ~LBF_ALL_PINNED; if (task_running(env->src_rq, p)) { schedstat_inc(p->se.statistics.nr_failed_migrations_running); return 0; } /* * Aggressive migration if: * 1) destination numa is preferred * 2) task is cache cold, or * 3) too many balance attempts have failed. */ 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->se.statistics.nr_forced_migrations); } return 1; } schedstat_inc(p->se.statistics.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_held(&env->src_rq->lock); p->on_rq = TASK_ON_RQ_MIGRATING; 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_held(&env->src_rq->lock); 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; } static const unsigned int sched_nr_migrate_break = 32; /* * detach_tasks() -- tries to detach up to imbalance weighted load 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; struct task_struct *p; unsigned long load; int detached = 0; lockdep_assert_held(&env->src_rq->lock); 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; p = list_last_entry(tasks, struct task_struct, se.group_node); env->loop++; /* We've more or less seen every task there is, call it quits */ if (env->loop > env->loop_max) 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; } if (!can_migrate_task(p, env)) goto next; load = task_h_load(p); if (sched_feat(LB_MIN) && load < 16 && !env->sd->nr_balance_failed) goto next; if ((load / 2) > env->imbalance) goto next; detach_task(p, env); list_add(&p->se.group_node, &env->tasks); detached++; env->imbalance -= load; #ifdef CONFIG_PREEMPT /* * 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 * weighted load. */ 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_held(&rq->lock); BUG_ON(task_rq(p) != rq); activate_task(rq, p, ENQUEUE_NOCLOCK); p->on_rq = TASK_ON_RQ_QUEUED; check_preempt_curr(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); } 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 defined(CONFIG_IRQ_TIME_ACCOUNTING) || defined(CONFIG_PARAVIRT_TIME_ACCOUNTING) if (READ_ONCE(rq->avg_irq.util_avg)) return true; #endif return false; } #ifdef CONFIG_FAIR_GROUP_SCHED static inline bool cfs_rq_is_decayed(struct cfs_rq *cfs_rq) { if (cfs_rq->load.weight) return false; if (cfs_rq->avg.load_sum) return false; if (cfs_rq->avg.util_sum) return false; if (cfs_rq->avg.runnable_load_sum) return false; return true; } static void update_blocked_averages(int cpu) { struct rq *rq = cpu_rq(cpu); struct cfs_rq *cfs_rq, *pos; const struct sched_class *curr_class; struct rq_flags rf; bool done = true; rq_lock_irqsave(rq, &rf); update_rq_clock(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; /* throttled entities do not contribute to load */ if (throttled_hierarchy(cfs_rq)) continue; if (update_cfs_rq_load_avg(cfs_rq_clock_task(cfs_rq), cfs_rq)) update_tg_load_avg(cfs_rq, 0); /* 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, 0); /* * 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; } curr_class = rq->curr->sched_class; update_rt_rq_load_avg(rq_clock_task(rq), rq, curr_class == &rt_sched_class); update_dl_rq_load_avg(rq_clock_task(rq), rq, curr_class == &dl_sched_class); update_irq_load_avg(rq, 0); /* Don't need periodic decay once load/util_avg are null */ if (others_have_blocked(rq)) done = false; #ifdef CONFIG_NO_HZ_COMMON rq->last_blocked_load_update_tick = jiffies; if (done) rq->has_blocked_load = 0; #endif rq_unlock_irqrestore(rq, &rf); } /* * 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; cfs_rq->h_load_next = NULL; for_each_sched_entity(se) { cfs_rq = cfs_rq_of(se); 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 = 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 inline void update_blocked_averages(int cpu) { struct rq *rq = cpu_rq(cpu); struct cfs_rq *cfs_rq = &rq->cfs; const struct sched_class *curr_class; struct rq_flags rf; rq_lock_irqsave(rq, &rf); update_rq_clock(rq); update_cfs_rq_load_avg(cfs_rq_clock_task(cfs_rq), cfs_rq); curr_class = rq->curr->sched_class; update_rt_rq_load_avg(rq_clock_task(rq), rq, curr_class == &rt_sched_class); update_dl_rq_load_avg(rq_clock_task(rq), rq, curr_class == &dl_sched_class); update_irq_load_avg(rq, 0); #ifdef CONFIG_NO_HZ_COMMON rq->last_blocked_load_update_tick = jiffies; if (!cfs_rq_has_blocked(cfs_rq) && !others_have_blocked(rq)) rq->has_blocked_load = 0; #endif rq_unlock_irqrestore(rq, &rf); } static unsigned long task_h_load(struct task_struct *p) { return p->se.avg.load_avg; } #endif /********** Helpers for find_busiest_group ************************/ enum group_type { group_other = 0, group_imbalanced, group_overloaded, }; /* * 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 sum_weighted_load; /* Weighted load of group's tasks */ unsigned long load_per_task; unsigned long group_capacity; unsigned long group_util; /* Total utilization of the group */ unsigned int sum_nr_running; /* Nr tasks running in the group */ unsigned int idle_cpus; unsigned int group_weight; enum group_type group_type; int group_no_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_running; 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 */ 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 clear busiest_stat::avg_load because * update_sd_pick_busiest() reads this before assignment. */ *sds = (struct sd_lb_stats){ .busiest = NULL, .local = NULL, .total_running = 0UL, .total_load = 0UL, .total_capacity = 0UL, .busiest_stat = { .avg_load = 0UL, .sum_nr_running = 0, .group_type = group_other, }, }; } /** * get_sd_load_idx - Obtain the load index for a given sched domain. * @sd: The sched_domain whose load_idx is to be obtained. * @idle: The idle status of the CPU for whose sd load_idx is obtained. * * Return: The load index. */ static inline int get_sd_load_idx(struct sched_domain *sd, enum cpu_idle_type idle) { int load_idx; switch (idle) { case CPU_NOT_IDLE: load_idx = sd->busy_idx; break; case CPU_NEWLY_IDLE: load_idx = sd->newidle_idx; break; default: load_idx = sd->idle_idx; break; } return load_idx; } static unsigned long scale_rt_capacity(struct sched_domain *sd, int cpu) { struct rq *rq = cpu_rq(cpu); unsigned long max = arch_scale_cpu_capacity(sd, cpu); unsigned long used, free; unsigned long irq; irq = cpu_util_irq(rq); if (unlikely(irq >= max)) return 1; used = READ_ONCE(rq->avg_rt.util_avg); used += READ_ONCE(rq->avg_dl.util_avg); 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(sd, cpu); struct sched_group *sdg = sd->groups; cpu_rq(cpu)->cpu_capacity_orig = arch_scale_cpu_capacity(sd, cpu); if (!capacity) capacity = 1; cpu_rq(cpu)->cpu_capacity = capacity; sdg->sgc->capacity = capacity; sdg->sgc->min_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; 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; 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)) { struct sched_group_capacity *sgc; struct rq *rq = cpu_rq(cpu); /* * build_sched_domains() -> init_sched_groups_capacity() * gets here before we've attached the domains to the * runqueues. * * Use capacity_of(), which is set irrespective of domains * in update_cpu_capacity(). * * This avoids capacity from being 0 and * causing divide-by-zero issues on boot. */ if (unlikely(!rq->sd)) { capacity += capacity_of(cpu); } else { sgc = rq->sd->groups->sgc; capacity += sgc->capacity; } min_capacity = min(capacity, min_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); group = group->next; } while (group != child->groups); } sdg->sgc->capacity = capacity; sdg->sgc->min_capacity = min_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) < (rq->cpu_capacity_orig * 100)); } /* * Group imbalance indicates (and tries to solve) the problem where balancing * groups is inadequate due to ->cpus_allowed 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(struct lb_env *env, struct sg_lb_stats *sgs) { if (sgs->sum_nr_running < sgs->group_weight) return true; if ((sgs->group_capacity * 100) > (sgs->group_util * env->sd->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(struct lb_env *env, struct sg_lb_stats *sgs) { if (sgs->sum_nr_running <= sgs->group_weight) return false; if ((sgs->group_capacity * 100) < (sgs->group_util * env->sd->imbalance_pct)) return true; return false; } /* * group_smaller_cpu_capacity: Returns true if sched_group sg has smaller * per-CPU capacity than sched_group ref. */ static inline bool group_smaller_cpu_capacity(struct sched_group *sg, struct sched_group *ref) { return sg->sgc->min_capacity * capacity_margin < ref->sgc->min_capacity * 1024; } static inline enum group_type group_classify(struct sched_group *group, struct sg_lb_stats *sgs) { if (sgs->group_no_capacity) return group_overloaded; if (sg_imbalanced(group)) return group_imbalanced; return group_other; } static bool update_nohz_stats(struct rq *rq, bool force) { #ifdef CONFIG_NO_HZ_COMMON unsigned int cpu = rq->cpu; if (!rq->has_blocked_load) return false; if (!cpumask_test_cpu(cpu, nohz.idle_cpus_mask)) return false; if (!force && !time_after(jiffies, rq->last_blocked_load_update_tick)) return true; update_blocked_averages(cpu); return rq->has_blocked_load; #else return false; #endif } /** * update_sg_lb_stats - Update sched_group's statistics for load balancing. * @env: The load balancing environment. * @group: sched_group whose statistics are to be updated. * @load_idx: Load index of sched_domain of this_cpu for load calc. * @local_group: Does group contain this_cpu. * @sgs: variable to hold the statistics for this group. * @overload: Indicate more than one runnable task for any CPU. */ static inline void update_sg_lb_stats(struct lb_env *env, struct sched_group *group, int load_idx, int local_group, struct sg_lb_stats *sgs, bool *overload) { unsigned long load; int i, nr_running; memset(sgs, 0, sizeof(*sgs)); for_each_cpu_and(i, sched_group_span(group), env->cpus) { struct rq *rq = cpu_rq(i); if ((env->flags & LBF_NOHZ_STATS) && update_nohz_stats(rq, false)) env->flags |= LBF_NOHZ_AGAIN; /* Bias balancing toward CPUs of our domain: */ if (local_group) load = target_load(i, load_idx); else load = source_load(i, load_idx); sgs->group_load += load; sgs->group_util += cpu_util(i); sgs->sum_nr_running += rq->cfs.h_nr_running; nr_running = rq->nr_running; if (nr_running > 1) *overload = true; #ifdef CONFIG_NUMA_BALANCING sgs->nr_numa_running += rq->nr_numa_running; sgs->nr_preferred_running += rq->nr_preferred_running; #endif sgs->sum_weighted_load += weighted_cpuload(rq); /* * No need to call idle_cpu() if nr_running is not 0 */ if (!nr_running && idle_cpu(i)) sgs->idle_cpus++; } /* Adjust by relative CPU capacity of the group */ sgs->group_capacity = group->sgc->capacity; sgs->avg_load = (sgs->group_load*SCHED_CAPACITY_SCALE) / sgs->group_capacity; if (sgs->sum_nr_running) sgs->load_per_task = sgs->sum_weighted_load / sgs->sum_nr_running; sgs->group_weight = group->group_weight; sgs->group_no_capacity = group_is_overloaded(env, sgs); sgs->group_type = group_classify(group, sgs); } /** * 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; if (sgs->group_type > busiest->group_type) return true; if (sgs->group_type < busiest->group_type) return false; if (sgs->avg_load <= busiest->avg_load) return false; if (!(env->sd->flags & SD_ASYM_CPUCAPACITY)) goto asym_packing; /* * 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 (sgs->sum_nr_running <= sgs->group_weight && group_smaller_cpu_capacity(sds->local, sg)) return false; asym_packing: /* This is the busiest node in its class. */ if (!(env->sd->flags & SD_ASYM_PACKING)) return true; /* No ASYM_PACKING if target CPU is already busy */ if (env->idle == CPU_NOT_IDLE) return true; /* * ASYM_PACKING needs to move all the work to the highest * prority CPUs in the group, therefore mark all groups * of lower priority than ourself as busy. */ if (sgs->sum_nr_running && sched_asym_prefer(env->dst_cpu, sg->asym_prefer_cpu)) { if (!sds->busiest) return true; /* Prefer to move from lowest priority CPU's work */ if (sched_asym_prefer(sds->busiest->asym_prefer_cpu, sg->asym_prefer_cpu)) return true; } return false; } #ifdef CONFIG_NUMA_BALANCING static inline enum fbq_type fbq_classify_group(struct sg_lb_stats *sgs) { if (sgs->sum_nr_running > sgs->nr_numa_running) return regular; if (sgs->sum_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 */ /** * 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_domain *child = env->sd->child; struct sched_group *sg = env->sd->groups; struct sg_lb_stats *local = &sds->local_stat; struct sg_lb_stats tmp_sgs; int load_idx, prefer_sibling = 0; bool overload = false; if (child && child->flags & SD_PREFER_SIBLING) prefer_sibling = 1; #ifdef CONFIG_NO_HZ_COMMON if (env->idle == CPU_NEWLY_IDLE && READ_ONCE(nohz.has_blocked)) env->flags |= LBF_NOHZ_STATS; #endif load_idx = get_sd_load_idx(env->sd, env->idle); 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, sg, load_idx, local_group, sgs, &overload); if (local_group) goto next_group; /* * In case the child domain prefers tasks go to siblings * first, lower the sg capacity so that we'll try * and move all the excess tasks away. We lower the capacity * of a group only if the local group has the capacity to fit * these excess tasks. The extra check prevents the case where * you always pull from the heaviest group when it is already * under-utilized (possible with a large weight task outweighs * the tasks on the system). */ if (prefer_sibling && sds->local && group_has_capacity(env, local) && (sgs->sum_nr_running > local->sum_nr_running + 1)) { sgs->group_no_capacity = 1; sgs->group_type = group_classify(sg, sgs); } 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_running += sgs->sum_nr_running; sds->total_load += sgs->group_load; sds->total_capacity += sgs->group_capacity; sg = sg->next; } while (sg != env->sd->groups); #ifdef CONFIG_NO_HZ_COMMON if ((env->flags & LBF_NOHZ_AGAIN) && cpumask_subset(nohz.idle_cpus_mask, sched_domain_span(env->sd))) { WRITE_ONCE(nohz.next_blocked, jiffies + msecs_to_jiffies(LOAD_AVG_PERIOD)); } #endif if (env->sd->flags & SD_NUMA) env->fbq_type = fbq_classify_group(&sds->busiest_stat); if (!env->sd->parent) { /* update overload indicator if we are at root domain */ if (env->dst_rq->rd->overload != overload) env->dst_rq->rd->overload = overload; } } /** * check_asym_packing - Check to see if the group is packed into the * sched domain. * * This is primarily intended to used at the sibling level. Some * cores like POWER7 prefer to use lower numbered SMT threads. In the * case of POWER7, it can move to lower SMT modes only when higher * threads are idle. When in lower SMT modes, the threads will * perform better since they share less core resources. Hence when we * have idle threads, we want them to be the higher ones. * * This packing function is run on idle threads. It checks to see if * the busiest CPU in this domain (core in the P7 case) has a higher * CPU number than the packing function is being run on. Here we are * assuming lower CPU number will be equivalent to lower a SMT thread * number. * * Return: 1 when packing is required and a task should be moved to * this CPU. The amount of the imbalance is returned in env->imbalance. * * @env: The load balancing environment. * @sds: Statistics of the sched_domain which is to be packed */ static int check_asym_packing(struct lb_env *env, struct sd_lb_stats *sds) { int busiest_cpu; if (!(env->sd->flags & SD_ASYM_PACKING)) return 0; if (env->idle == CPU_NOT_IDLE) return 0; if (!sds->busiest) return 0; busiest_cpu = sds->busiest->asym_prefer_cpu; if (sched_asym_prefer(busiest_cpu, env->dst_cpu)) return 0; env->imbalance = DIV_ROUND_CLOSEST( sds->busiest_stat.avg_load * sds->busiest_stat.group_capacity, SCHED_CAPACITY_SCALE); return 1; } /** * fix_small_imbalance - Calculate the minor imbalance that exists * amongst the groups of a sched_domain, during * load balancing. * @env: The load balancing environment. * @sds: Statistics of the sched_domain whose imbalance is to be calculated. */ static inline void fix_small_imbalance(struct lb_env *env, struct sd_lb_stats *sds) { unsigned long tmp, capa_now = 0, capa_move = 0; unsigned int imbn = 2; unsigned long scaled_busy_load_per_task; struct sg_lb_stats *local, *busiest; local = &sds->local_stat; busiest = &sds->busiest_stat; if (!local->sum_nr_running) local->load_per_task = cpu_avg_load_per_task(env->dst_cpu); else if (busiest->load_per_task > local->load_per_task) imbn = 1; scaled_busy_load_per_task = (busiest->load_per_task * SCHED_CAPACITY_SCALE) / busiest->group_capacity; if (busiest->avg_load + scaled_busy_load_per_task >= local->avg_load + (scaled_busy_load_per_task * imbn)) { env->imbalance = busiest->load_per_task; return; } /* * OK, we don't have enough imbalance to justify moving tasks, * however we may be able to increase total CPU capacity used by * moving them. */ capa_now += busiest->group_capacity * min(busiest->load_per_task, busiest->avg_load); capa_now += local->group_capacity * min(local->load_per_task, local->avg_load); capa_now /= SCHED_CAPACITY_SCALE; /* Amount of load we'd subtract */ if (busiest->avg_load > scaled_busy_load_per_task) { capa_move += busiest->group_capacity * min(busiest->load_per_task, busiest->avg_load - scaled_busy_load_per_task); } /* Amount of load we'd add */ if (busiest->avg_load * busiest->group_capacity < busiest->load_per_task * SCHED_CAPACITY_SCALE) { tmp = (busiest->avg_load * busiest->group_capacity) / local->group_capacity; } else { tmp = (busiest->load_per_task * SCHED_CAPACITY_SCALE) / local->group_capacity; } capa_move += local->group_capacity * min(local->load_per_task, local->avg_load + tmp); capa_move /= SCHED_CAPACITY_SCALE; /* Move if we gain throughput */ if (capa_move > capa_now) env->imbalance = busiest->load_per_task; } /** * 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) { unsigned long max_pull, load_above_capacity = ~0UL; struct sg_lb_stats *local, *busiest; local = &sds->local_stat; busiest = &sds->busiest_stat; if (busiest->group_type == group_imbalanced) { /* * In the group_imb case we cannot rely on group-wide averages * to ensure CPU-load equilibrium, look at wider averages. XXX */ busiest->load_per_task = min(busiest->load_per_task, sds->avg_load); } /* * Avg load of busiest sg can be less and avg load of local sg can * be greater than avg load across all sgs of sd because avg load * factors in sg capacity and sgs with smaller group_type are * skipped when updating the busiest sg: */ if (busiest->avg_load <= sds->avg_load || local->avg_load >= sds->avg_load) { env->imbalance = 0; return fix_small_imbalance(env, sds); } /* * If there aren't any idle CPUs, avoid creating some. */ if (busiest->group_type == group_overloaded && local->group_type == group_overloaded) { load_above_capacity = busiest->sum_nr_running * SCHED_CAPACITY_SCALE; if (load_above_capacity > busiest->group_capacity) { load_above_capacity -= busiest->group_capacity; load_above_capacity *= scale_load_down(NICE_0_LOAD); load_above_capacity /= busiest->group_capacity; } else load_above_capacity = ~0UL; } /* * 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. */ max_pull = min(busiest->avg_load - sds->avg_load, load_above_capacity); /* How much load to actually move to equalise the imbalance */ env->imbalance = min( max_pull * busiest->group_capacity, (sds->avg_load - local->avg_load) * local->group_capacity ) / SCHED_CAPACITY_SCALE; /* * if *imbalance is less than the average load per runnable task * there is no guarantee that any tasks will be moved so we'll have * a think about bumping its value to force at least one task to be * moved */ if (env->imbalance < busiest->load_per_task) return fix_small_imbalance(env, sds); } /******* find_busiest_group() helpers end here *********************/ /** * find_busiest_group - Returns the busiest group within the sched_domain * if there is an imbalance. * * Also calculates the amount of weighted load which should be moved * to restore balance. * * @env: The load balancing environment. * * 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 relavent for load balancing at * this level. */ update_sd_lb_stats(env, &sds); local = &sds.local_stat; busiest = &sds.busiest_stat; /* ASYM feature bypasses nice load balance check */ if (check_asym_packing(env, &sds)) return sds.busiest; /* There is no busy sibling group to pull tasks from */ if (!sds.busiest || busiest->sum_nr_running == 0) goto out_balanced; /* XXX broken for overlapping NUMA groups */ sds.avg_load = (SCHED_CAPACITY_SCALE * sds.total_load) / sds.total_capacity; /* * 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_allowed constraints and the like. */ if (busiest->group_type == group_imbalanced) goto force_balance; /* * When dst_cpu is idle, prevent SMP nice and/or asymmetric group * capacities from resulting in underutilization due to avg_load. */ if (env->idle != CPU_NOT_IDLE && group_has_capacity(env, local) && busiest->group_no_capacity) goto force_balance; /* * If the local group is busier than the selected busiest group * don't try and pull any tasks. */ if (local->avg_load >= busiest->avg_load) goto out_balanced; /* * 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 (env->idle == CPU_IDLE) { /* * This CPU is idle. 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 */ if ((busiest->group_type != group_overloaded) && (local->idle_cpus <= (busiest->idle_cpus + 1))) goto out_balanced; } else { /* * In the CPU_NEWLY_IDLE, CPU_NOT_IDLE cases, use * imbalance_pct to be conservative. */ if (100 * busiest->avg_load <= env->sd->imbalance_pct * local->avg_load) 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_load = 0, busiest_capacity = 1; int i; for_each_cpu_and(i, sched_group_span(group), env->cpus) { unsigned long capacity, wl; 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; capacity = capacity_of(i); wl = weighted_cpuload(rq); /* * When comparing with imbalance, use weighted_cpuload() * which is not scaled with the CPU capacity. */ if (rq->nr_running == 1 && wl > env->imbalance && !check_cpu_capacity(rq, env->sd)) continue; /* * For the load comparisons with the other CPU's, consider * the weighted_cpuload() 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(wl_i / capacity_i), crosswise * multiplication to rid ourselves of the division works out * to: wl_i * capacity_j > wl_j * capacity_i; where j is * our previous maximum. */ if (wl * busiest_capacity > busiest_load * capacity) { busiest_load = wl; busiest_capacity = capacity; busiest = rq; } } 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 int need_active_balance(struct lb_env *env) { struct sched_domain *sd = env->sd; if (env->idle == CPU_NEWLY_IDLE) { /* * ASYM_PACKING needs to force migrate tasks from busy but * lower priority CPUs in order to pack all tasks in the * highest priority CPUs. */ if ((sd->flags & SD_ASYM_PACKING) && sched_asym_prefer(env->dst_cpu, env->src_cpu)) 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; } return unlikely(sd->nr_balance_failed > sd->cache_nice_tries+2); } static int active_load_balance_cpu_stop(void *data); static int should_we_balance(struct lb_env *env) { struct sched_group *sg = env->sd->groups; int cpu, balance_cpu = -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. */ if (env->idle == CPU_NEWLY_IDLE) return 1; /* Try to find first idle CPU */ for_each_cpu_and(cpu, group_balance_mask(sg), env->cpus) { if (!idle_cpu(cpu)) continue; balance_cpu = cpu; break; } if (balance_cpu == -1) balance_cpu = group_balance_cpu(sg); /* * First idle CPU or the first CPU(busiest) in this sched group * is eligible for doing load balancing at this and above domains. */ return balance_cpu == 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 = sched_group_span(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; } BUG_ON(busiest == env.dst_rq); schedstat_add(sd->lb_imbalance[idle], env.imbalance); env.src_cpu = busiest->cpu; env.src_rq = busiest; ld_moved = 0; 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.flags |= LBF_ALL_PINNED; 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; 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 exceess 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_lock_irqsave(&busiest->lock, 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_allowed)) { raw_spin_unlock_irqrestore(&busiest->lock, flags); env.flags |= LBF_ALL_PINNED; goto out_one_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; } raw_spin_unlock_irqrestore(&busiest->lock, flags); if (active_balance) { stop_one_cpu_nowait(cpu_of(busiest), active_load_balance_cpu_stop, busiest, &busiest->active_balance_work); } /* We've kicked active balancing, force task migration. */ sd->nr_balance_failed = sd->cache_nice_tries+1; } } else sd->nr_balance_failed = 0; if (likely(!active_balance)) { /* We were unbalanced, so reset the balancing interval */ sd->balance_interval = sd->min_interval; } else { /* * If we've begun active balancing, start to back off. This * case may not be covered by the all_pinned logic if there * is only 1 task on the busy runqueue (because we don't call * detach_tasks). */ if (sd->balance_interval < sd->max_interval) sd->balance_interval *= 2; } goto out; out_balanced: /* * We reach balance although we may have faced some affinity * constraints. Clear the imbalance flag if it was set. */ if (sd_parent) { 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: /* 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; ld_moved = 0; 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); 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. */ BUG_ON(busiest_rq == target_rq); /* Search for an sd spanning us and the target CPU. */ rcu_read_lock(); for_each_domain(target_cpu, sd) { if ((sd->flags & SD_LOAD_BALANCE) && 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, /* * can_migrate_task() doesn't need to compute new_dst_cpu * for active balancing. Since we have CPU_IDLE, but no * @dst_grpmask we need to make that test go away with lying * about DST_PINNED. */ .flags = LBF_DST_PINNED, }; 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; } /* * 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; 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. Decay ~1% per second. */ if (time_after(jiffies, sd->next_decay_max_lb_cost)) { sd->max_newidle_lb_cost = (sd->max_newidle_lb_cost * 253) / 256; sd->next_decay_max_lb_cost = jiffies + HZ; need_decay = 1; } max_cost += sd->max_newidle_lb_cost; if (!(sd->flags & SD_LOAD_BALANCE)) continue; /* * 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, idle != CPU_IDLE); 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; } sd->last_balance = jiffies; interval = get_sd_balance_interval(sd, idle != CPU_IDLE); } 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; #ifdef CONFIG_NO_HZ_COMMON /* * If this CPU has been elected to perform the nohz idle * balance. Other idle CPUs have already rebalanced with * nohz_idle_balance() and nohz.next_balance has been * updated accordingly. This CPU is now running the idle load * balance for itself and we need to update the * nohz.next_balance accordingly. */ if ((idle == CPU_IDLE) && time_after(nohz.next_balance, rq->next_balance)) nohz.next_balance = rq->next_balance; #endif } } static inline int on_null_domain(struct rq *rq) { return unlikely(!rcu_dereference_sched(rq->sd)); } #ifdef CONFIG_NO_HZ_COMMON /* * idle load balancing details * - When one of the busy CPUs notice 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. */ static inline int find_new_ilb(void) { int ilb = cpumask_first(nohz.idle_cpus_mask); if (ilb < nr_cpu_ids && idle_cpu(ilb)) return ilb; return nr_cpu_ids; } /* * Kick a CPU to do the nohz balancing, if it is time for it. We pick the * nohz_load_balancer CPU (if there is one) otherwise fallback to any idle * CPU (if there is one). */ static void kick_ilb(unsigned int flags) { int ilb_cpu; nohz.next_balance++; ilb_cpu = find_new_ilb(); if (ilb_cpu >= nr_cpu_ids) return; flags = atomic_fetch_or(flags, nohz_flags(ilb_cpu)); if (flags & NOHZ_KICK_MASK) return; /* * Use smp_send_reschedule() instead of resched_cpu(). * This way we generate a sched IPI on the target CPU which * is idle. And the softirq performing nohz idle load balance * will be run before returning from the IPI. */ smp_send_reschedule(ilb_cpu); } /* * Current heuristic for kicking the idle load balancer in the presence * of an idle cpu in the system. * - This rq has more than one task. * - This rq has at least one CFS task and the capacity of the CPU is * significantly reduced because of RT tasks or IRQs. * - At parent of LLC scheduler domain level, this cpu's scheduler group has * multiple busy cpu. * - For SD_ASYM_PACKING, if the lower numbered cpu's in the scheduler * domain span are idle. */ 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_KICK_MASK; goto out; } rcu_read_lock(); sds = rcu_dereference(per_cpu(sd_llc_shared, cpu)); if (sds) { /* * XXX: write a coherent comment on why we do this. * See also: http://lkml.kernel.org/r/20111202010832.602203411@sbsiddha-desk.sc.intel.com */ nr_busy = atomic_read(&sds->nr_busy_cpus); if (nr_busy > 1) { flags = NOHZ_KICK_MASK; goto unlock; } } sd = rcu_dereference(rq->sd); if (sd) { if ((rq->cfs.h_nr_running >= 1) && check_cpu_capacity(rq, sd)) { flags = NOHZ_KICK_MASK; goto unlock; } } sd = rcu_dereference(per_cpu(sd_asym, cpu)); if (sd) { for_each_cpu(i, sched_domain_span(sd)) { if (i == cpu || !cpumask_test_cpu(i, nohz.idle_cpus_mask)) continue; if (sched_asym_prefer(i, cpu)) { flags = NOHZ_KICK_MASK; goto unlock; } } } unlock: rcu_read_unlock(); out: 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_FLAG_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 * store. */ smp_mb__after_atomic(); set_cpu_sd_state_idle(cpu); 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); } /* * 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. * The function returns false if the loop has stopped before running * through all idle CPUs. */ static bool _nohz_idle_balance(struct rq *this_rq, unsigned int flags, enum cpu_idle_type idle) { /* 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; int ret = false; 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 trig 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. */ WRITE_ONCE(nohz.has_blocked, 0); /* * Ensures that if we miss the CPU, we must see the has_blocked * store from nohz_balance_enter_idle(). */ smp_mb(); for_each_cpu(balance_cpu, nohz.idle_cpus_mask) { if (balance_cpu == this_cpu || !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()) { has_blocked_load = true; goto abort; } rq = cpu_rq(balance_cpu); has_blocked_load |= update_nohz_stats(rq, true); /* * 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); cpu_load_update_idle(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; } } /* Newly idle CPU doesn't need an update */ if (idle != CPU_NEWLY_IDLE) { update_blocked_averages(this_cpu); has_blocked_load |= this_rq->has_blocked_load; } if (flags & NOHZ_BALANCE_KICK) rebalance_domains(this_rq, CPU_IDLE); WRITE_ONCE(nohz.next_blocked, now + msecs_to_jiffies(LOAD_AVG_PERIOD)); /* The full idle balance loop has been done */ ret = true; abort: /* There is still blocked load, enable periodic update */ if (has_blocked_load) WRITE_ONCE(nohz.has_blocked, 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; return ret; } /* * 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) { int this_cpu = this_rq->cpu; unsigned int flags; if (!(atomic_read(nohz_flags(this_cpu)) & NOHZ_KICK_MASK)) return false; if (idle != CPU_IDLE) { atomic_andnot(NOHZ_KICK_MASK, nohz_flags(this_cpu)); return false; } /* * barrier, pairs with nohz_balance_enter_idle(), ensures ... */ flags = atomic_fetch_andnot(NOHZ_KICK_MASK, nohz_flags(this_cpu)); if (!(flags & NOHZ_KICK_MASK)) return false; _nohz_idle_balance(this_rq, flags, idle); return true; } 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_FLAG_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; raw_spin_unlock(&this_rq->lock); /* * This CPU is going to be idle and blocked load of idle CPUs * need to be updated. Run the ilb locally as it is a good * candidate for ilb instead of waking up another idle CPU. * Kick an normal ilb if we failed to do the update. */ if (!_nohz_idle_balance(this_rq, NOHZ_STATS_KICK, CPU_NEWLY_IDLE)) kick_ilb(NOHZ_STATS_KICK); raw_spin_lock(&this_rq->lock); } #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 */ /* * idle_balance is called by schedule() if this_cpu is about to become * idle. Attempts to pull tasks from other CPUs. */ static int idle_balance(struct rq *this_rq, struct rq_flags *rf) { unsigned long next_balance = jiffies + HZ; int this_cpu = this_rq->cpu; struct sched_domain *sd; int pulled_task = 0; u64 curr_cost = 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); if (this_rq->avg_idle < sysctl_sched_migration_cost || !this_rq->rd->overload) { rcu_read_lock(); sd = rcu_dereference_check_sched_domain(this_rq->sd); if (sd) update_next_balance(sd, &next_balance); rcu_read_unlock(); nohz_newidle_balance(this_rq); goto out; } raw_spin_unlock(&this_rq->lock); update_blocked_averages(this_cpu); rcu_read_lock(); for_each_domain(this_cpu, sd) { int continue_balancing = 1; u64 t0, domain_cost; if (!(sd->flags & SD_LOAD_BALANCE)) continue; if (this_rq->avg_idle < curr_cost + sd->max_newidle_lb_cost) { update_next_balance(sd, &next_balance); break; } if (sd->flags & SD_BALANCE_NEWIDLE) { t0 = sched_clock_cpu(this_cpu); pulled_task = load_balance(this_cpu, this_rq, sd, CPU_NEWLY_IDLE, &continue_balancing); domain_cost = sched_clock_cpu(this_cpu) - t0; if (domain_cost > sd->max_newidle_lb_cost) sd->max_newidle_lb_cost = domain_cost; curr_cost += domain_cost; } update_next_balance(sd, &next_balance); /* * Stop searching for tasks to pull if there are * now runnable tasks on this rq. */ if (pulled_task || this_rq->nr_running > 0) break; } rcu_read_unlock(); raw_spin_lock(&this_rq->lock); if (curr_cost > this_rq->max_idle_balance_cost) this_rq->max_idle_balance_cost = curr_cost; out: /* * 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; /* Move the next balance forward */ if (time_after(this_rq->next_balance, next_balance)) this_rq->next_balance = next_balance; /* Is there a task of a high priority class? */ if (this_rq->nr_running != this_rq->cfs.h_nr_running) pulled_task = -1; if (pulled_task) this_rq->idle_stamp = 0; 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 */ if (unlikely(on_null_domain(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 */ /* * 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); } /* * 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 cfs_rq *cfs_rq; struct sched_entity *se = &p->se, *curr; 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); se->vruntime = curr->vruntime; } place_entity(cfs_rq, se, 1); if (sysctl_sched_child_runs_first && curr && entity_before(curr, se)) { /* * Upon rescheduling, sched_class::put_prev_task() will place * 'current' within the tree based on its new key value. */ swap(curr->vruntime, se->vruntime); resched_curr(rq); } se->vruntime -= cfs_rq->min_vruntime; 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; /* * 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 (rq->curr == p) { if (p->prio > oldprio) resched_curr(rq); } else check_preempt_curr(rq, p, 0); } static inline bool vruntime_normalized(struct task_struct *p) { struct sched_entity *se = &p->se; /* * In both the TASK_ON_RQ_QUEUED and TASK_ON_RQ_MIGRATING cases, * the dequeue_entity(.flags=0) will already have normalized the * vruntime. */ if (p->on_rq) return true; /* * When !on_rq, vruntime of the task has usually NOT been normalized. * But there are some cases where it has already been normalized: * * - A forked child which is waiting for being woken up by * wake_up_new_task(). * - A task which has been woken up by try_to_wake_up() and * waiting for actually being woken up by sched_ttwu_pending(). */ if (!se->sum_exec_runtime || (p->state == TASK_WAKING && p->sched_remote_wakeup)) return true; return false; } #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; /* Start to propagate at parent */ se = se->parent; for_each_sched_entity(se) { cfs_rq = cfs_rq_of(se); if (cfs_rq_throttled(cfs_rq)) break; update_load_avg(cfs_rq, se, UPDATE_TG); } } #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); /* 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, false); propagate_entity_cfs_rq(se); } static void attach_entity_cfs_rq(struct sched_entity *se) { struct cfs_rq *cfs_rq = cfs_rq_of(se); #ifdef CONFIG_FAIR_GROUP_SCHED /* * Since the real-depth could have been changed (only FAIR * class maintain depth value), reset depth properly. */ se->depth = se->parent ? se->parent->depth + 1 : 0; #endif /* 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, 0); update_tg_load_avg(cfs_rq, false); propagate_entity_cfs_rq(se); } static void detach_task_cfs_rq(struct task_struct *p) { struct sched_entity *se = &p->se; struct cfs_rq *cfs_rq = cfs_rq_of(se); if (!vruntime_normalized(p)) { /* * Fix up our vruntime so that the current sleep doesn't * cause 'unlimited' sleep bonus. */ place_entity(cfs_rq, se, 0); se->vruntime -= cfs_rq->min_vruntime; } detach_entity_cfs_rq(se); } static void attach_task_cfs_rq(struct task_struct *p) { struct sched_entity *se = &p->se; struct cfs_rq *cfs_rq = cfs_rq_of(se); attach_entity_cfs_rq(se); if (!vruntime_normalized(p)) se->vruntime += cfs_rq->min_vruntime; } 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 (rq->curr == p) resched_curr(rq); else check_preempt_curr(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_curr_task_fair(struct rq *rq) { struct sched_entity *se = &rq->curr->se; 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; cfs_rq->min_vruntime = (u64)(-(1LL << 20)); #ifndef CONFIG_64BIT cfs_rq->min_vruntime_copy = cfs_rq->min_vruntime; #endif #ifdef CONFIG_SMP raw_spin_lock_init(&cfs_rq->removed.lock); #endif } #ifdef CONFIG_FAIR_GROUP_SCHED static void task_set_group_fair(struct task_struct *p) { struct sched_entity *se = &p->se; set_task_rq(p, task_cpu(p)); se->depth = se->parent ? se->parent->depth + 1 : 0; } static void task_move_group_fair(struct task_struct *p) { detach_task_cfs_rq(p); set_task_rq(p, task_cpu(p)); #ifdef CONFIG_SMP /* Tell se's cfs_rq has been changed -- migrated */ p->se.avg.last_update_time = 0; #endif attach_task_cfs_rq(p); } static void task_change_group_fair(struct task_struct *p, int type) { switch (type) { case TASK_SET_GROUP: task_set_group_fair(p); break; case TASK_MOVE_GROUP: task_move_group_fair(p); break; } } void free_fair_sched_group(struct task_group *tg) { int i; destroy_cfs_bandwidth(tg_cfs_bandwidth(tg)); 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)); 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), 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 *rq; int i; for_each_possible_cpu(i) { rq = cpu_rq(i); se = tg->se[i]; raw_spin_lock_irq(&rq->lock); update_rq_clock(rq); attach_entity_cfs_rq(se); sync_throttle(tg, i); raw_spin_unlock_irq(&rq->lock); } } void unregister_fair_sched_group(struct task_group *tg) { unsigned long flags; struct rq *rq; int cpu; 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_lock_irqsave(&rq->lock, flags); list_del_leaf_cfs_rq(tg->cfs_rq[cpu]); raw_spin_unlock_irqrestore(&rq->lock, 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); int sched_group_set_shares(struct task_group *tg, unsigned long shares) { int i; /* * 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)); mutex_lock(&shares_mutex); if (tg->shares == shares) goto done; 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); } done: 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(sched_slice(cfs_rq_of(se), se)); return rr_interval; } /* * All the scheduling class methods: */ const struct sched_class fair_sched_class = { .next = &idle_sched_class, .enqueue_task = enqueue_task_fair, .dequeue_task = dequeue_task_fair, .yield_task = yield_task_fair, .yield_to_task = yield_to_task_fair, .check_preempt_curr = check_preempt_wakeup, .pick_next_task = pick_next_task_fair, .put_prev_task = put_prev_task_fair, #ifdef CONFIG_SMP .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 .set_curr_task = set_curr_task_fair, .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_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; 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 (p->numa_group) { gsf = p->numa_group->faults[task_faults_idx(NUMA_MEM, node, 0)], gpf = p->numa_group->faults[task_faults_idx(NUMA_MEM, node, 1)]; } print_numa_stats(m, node, tsf, tpf, gsf, gpf); } } #endif /* CONFIG_NUMA_BALANCING */ #endif /* CONFIG_SCHED_DEBUG */ __init void init_sched_fair_class(void) { #ifdef CONFIG_SMP 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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