| Author | Tokens | Token Proportion | Commits | Commit Proportion |
|---|---|---|---|---|
| Dan Magenheimer | 1546 | 84.95% | 3 | 17.65% |
| Jana Saout | 111 | 6.10% | 1 | 5.88% |
| Jingoo Han | 63 | 3.46% | 1 | 5.88% |
| Bob Liu | 36 | 1.98% | 2 | 11.76% |
| Kay Sievers | 36 | 1.98% | 1 | 5.88% |
| Joe Perches | 10 | 0.55% | 1 | 5.88% |
| Konrad Rzeszutek Wilk | 7 | 0.38% | 2 | 11.76% |
| Greg Kroah-Hartman | 4 | 0.22% | 2 | 11.76% |
| Arun K S | 3 | 0.16% | 1 | 5.88% |
| K. Y. Srinivasan | 2 | 0.11% | 1 | 5.88% |
| Mike Rapoport | 1 | 0.05% | 1 | 5.88% |
| Jan Beulich | 1 | 0.05% | 1 | 5.88% |
| Total | 1820 | 17 |
// SPDX-License-Identifier: GPL-2.0 /****************************************************************************** * Xen selfballoon driver (and optional frontswap self-shrinking driver) * * Copyright (c) 2009-2011, Dan Magenheimer, Oracle Corp. * * This code complements the cleancache and frontswap patchsets to optimize * support for Xen Transcendent Memory ("tmem"). The policy it implements * is rudimentary and will likely improve over time, but it does work well * enough today. * * Two functionalities are implemented here which both use "control theory" * (feedback) to optimize memory utilization. In a virtualized environment * such as Xen, RAM is often a scarce resource and we would like to ensure * that each of a possibly large number of virtual machines is using RAM * efficiently, i.e. using as little as possible when under light load * and obtaining as much as possible when memory demands are high. * Since RAM needs vary highly dynamically and sometimes dramatically, * "hysteresis" is used, that is, memory target is determined not just * on current data but also on past data stored in the system. * * "Selfballooning" creates memory pressure by managing the Xen balloon * driver to decrease and increase available kernel memory, driven * largely by the target value of "Committed_AS" (see /proc/meminfo). * Since Committed_AS does not account for clean mapped pages (i.e. pages * in RAM that are identical to pages on disk), selfballooning has the * affect of pushing less frequently used clean pagecache pages out of * kernel RAM and, presumably using cleancache, into Xen tmem where * Xen can more efficiently optimize RAM utilization for such pages. * * When kernel memory demand unexpectedly increases faster than Xen, via * the selfballoon driver, is able to (or chooses to) provide usable RAM, * the kernel may invoke swapping. In most cases, frontswap is able * to absorb this swapping into Xen tmem. However, due to the fact * that the kernel swap subsystem assumes swapping occurs to a disk, * swapped pages may sit on the disk for a very long time; even if * the kernel knows the page will never be used again. This is because * the disk space costs very little and can be overwritten when * necessary. When such stale pages are in frontswap, however, they * are taking up valuable real estate. "Frontswap selfshrinking" works * to resolve this: When frontswap activity is otherwise stable * and the guest kernel is not under memory pressure, the "frontswap * selfshrinking" accounts for this by providing pressure to remove some * pages from frontswap and return them to kernel memory. * * For both "selfballooning" and "frontswap-selfshrinking", a worker * thread is used and sysfs tunables are provided to adjust the frequency * and rate of adjustments to achieve the goal, as well as to disable one * or both functions independently. * * While some argue that this functionality can and should be implemented * in userspace, it has been observed that bad things happen (e.g. OOMs). * * System configuration note: Selfballooning should not be enabled on * systems without a sufficiently large swap device configured; for best * results, it is recommended that total swap be increased by the size * of the guest memory. Note, that selfballooning should be disabled by default * if frontswap is not configured. Similarly selfballooning should be enabled * by default if frontswap is configured and can be disabled with the * "tmem.selfballooning=0" kernel boot option. Finally, when frontswap is * configured, frontswap-selfshrinking can be disabled with the * "tmem.selfshrink=0" kernel boot option. * * Selfballooning is disallowed in domain0 and force-disabled. * */ #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt #include <linux/kernel.h> #include <linux/memblock.h> #include <linux/swap.h> #include <linux/mm.h> #include <linux/mman.h> #include <linux/workqueue.h> #include <linux/device.h> #include <xen/balloon.h> #include <xen/tmem.h> #include <xen/xen.h> /* Enable/disable with sysfs. */ static int xen_selfballooning_enabled __read_mostly; /* * Controls rate at which memory target (this iteration) approaches * ultimate goal when memory need is increasing (up-hysteresis) or * decreasing (down-hysteresis). Higher values of hysteresis cause * slower increases/decreases. The default values for the various * parameters were deemed reasonable by experimentation, may be * workload-dependent, and can all be adjusted via sysfs. */ static unsigned int selfballoon_downhysteresis __read_mostly = 8; static unsigned int selfballoon_uphysteresis __read_mostly = 1; /* In HZ, controls frequency of worker invocation. */ static unsigned int selfballoon_interval __read_mostly = 5; /* * Minimum usable RAM in MB for selfballooning target for balloon. * If non-zero, it is added to totalreserve_pages and self-ballooning * will not balloon below the sum. If zero, a piecewise linear function * is calculated as a minimum and added to totalreserve_pages. Note that * setting this value indiscriminately may cause OOMs and crashes. */ static unsigned int selfballoon_min_usable_mb; /* * Amount of RAM in MB to add to the target number of pages. * Can be used to reserve some more room for caches and the like. */ static unsigned int selfballoon_reserved_mb; static void selfballoon_process(struct work_struct *work); static DECLARE_DELAYED_WORK(selfballoon_worker, selfballoon_process); #ifdef CONFIG_FRONTSWAP #include <linux/frontswap.h> /* Enable/disable with sysfs. */ static bool frontswap_selfshrinking __read_mostly; /* * The default values for the following parameters were deemed reasonable * by experimentation, may be workload-dependent, and can all be * adjusted via sysfs. */ /* Control rate for frontswap shrinking. Higher hysteresis is slower. */ static unsigned int frontswap_hysteresis __read_mostly = 20; /* * Number of selfballoon worker invocations to wait before observing that * frontswap selfshrinking should commence. Note that selfshrinking does * not use a separate worker thread. */ static unsigned int frontswap_inertia __read_mostly = 3; /* Countdown to next invocation of frontswap_shrink() */ static unsigned long frontswap_inertia_counter; /* * Invoked by the selfballoon worker thread, uses current number of pages * in frontswap (frontswap_curr_pages()), previous status, and control * values (hysteresis and inertia) to determine if frontswap should be * shrunk and what the new frontswap size should be. Note that * frontswap_shrink is essentially a partial swapoff that immediately * transfers pages from the "swap device" (frontswap) back into kernel * RAM; despite the name, frontswap "shrinking" is very different from * the "shrinker" interface used by the kernel MM subsystem to reclaim * memory. */ static void frontswap_selfshrink(void) { static unsigned long cur_frontswap_pages; unsigned long last_frontswap_pages; unsigned long tgt_frontswap_pages; last_frontswap_pages = cur_frontswap_pages; cur_frontswap_pages = frontswap_curr_pages(); if (!cur_frontswap_pages || (cur_frontswap_pages > last_frontswap_pages)) { frontswap_inertia_counter = frontswap_inertia; return; } if (frontswap_inertia_counter && --frontswap_inertia_counter) return; if (cur_frontswap_pages <= frontswap_hysteresis) tgt_frontswap_pages = 0; else tgt_frontswap_pages = cur_frontswap_pages - (cur_frontswap_pages / frontswap_hysteresis); frontswap_shrink(tgt_frontswap_pages); frontswap_inertia_counter = frontswap_inertia; } #endif /* CONFIG_FRONTSWAP */ #define MB2PAGES(mb) ((mb) << (20 - PAGE_SHIFT)) #define PAGES2MB(pages) ((pages) >> (20 - PAGE_SHIFT)) /* * Use current balloon size, the goal (vm_committed_as), and hysteresis * parameters to set a new target balloon size */ static void selfballoon_process(struct work_struct *work) { unsigned long cur_pages, goal_pages, tgt_pages, floor_pages; unsigned long useful_pages; bool reset_timer = false; if (xen_selfballooning_enabled) { cur_pages = totalram_pages(); tgt_pages = cur_pages; /* default is no change */ goal_pages = vm_memory_committed() + totalreserve_pages + MB2PAGES(selfballoon_reserved_mb); #ifdef CONFIG_FRONTSWAP /* allow space for frontswap pages to be repatriated */ if (frontswap_selfshrinking) goal_pages += frontswap_curr_pages(); #endif if (cur_pages > goal_pages) tgt_pages = cur_pages - ((cur_pages - goal_pages) / selfballoon_downhysteresis); else if (cur_pages < goal_pages) tgt_pages = cur_pages + ((goal_pages - cur_pages) / selfballoon_uphysteresis); /* else if cur_pages == goal_pages, no change */ useful_pages = max_pfn - totalreserve_pages; if (selfballoon_min_usable_mb != 0) floor_pages = totalreserve_pages + MB2PAGES(selfballoon_min_usable_mb); /* piecewise linear function ending in ~3% slope */ else if (useful_pages < MB2PAGES(16)) floor_pages = max_pfn; /* not worth ballooning */ else if (useful_pages < MB2PAGES(64)) floor_pages = totalreserve_pages + MB2PAGES(16) + ((useful_pages - MB2PAGES(16)) >> 1); else if (useful_pages < MB2PAGES(512)) floor_pages = totalreserve_pages + MB2PAGES(40) + ((useful_pages - MB2PAGES(40)) >> 3); else /* useful_pages >= MB2PAGES(512) */ floor_pages = totalreserve_pages + MB2PAGES(99) + ((useful_pages - MB2PAGES(99)) >> 5); if (tgt_pages < floor_pages) tgt_pages = floor_pages; balloon_set_new_target(tgt_pages + balloon_stats.current_pages - totalram_pages()); reset_timer = true; } #ifdef CONFIG_FRONTSWAP if (frontswap_selfshrinking) { frontswap_selfshrink(); reset_timer = true; } #endif if (reset_timer) schedule_delayed_work(&selfballoon_worker, selfballoon_interval * HZ); } #ifdef CONFIG_SYSFS #include <linux/capability.h> #define SELFBALLOON_SHOW(name, format, args...) \ static ssize_t show_##name(struct device *dev, \ struct device_attribute *attr, \ char *buf) \ { \ return sprintf(buf, format, ##args); \ } SELFBALLOON_SHOW(selfballooning, "%d\n", xen_selfballooning_enabled); static ssize_t store_selfballooning(struct device *dev, struct device_attribute *attr, const char *buf, size_t count) { bool was_enabled = xen_selfballooning_enabled; unsigned long tmp; int err; if (!capable(CAP_SYS_ADMIN)) return -EPERM; err = kstrtoul(buf, 10, &tmp); if (err) return err; if ((tmp != 0) && (tmp != 1)) return -EINVAL; xen_selfballooning_enabled = !!tmp; if (!was_enabled && xen_selfballooning_enabled) schedule_delayed_work(&selfballoon_worker, selfballoon_interval * HZ); return count; } static DEVICE_ATTR(selfballooning, S_IRUGO | S_IWUSR, show_selfballooning, store_selfballooning); SELFBALLOON_SHOW(selfballoon_interval, "%d\n", selfballoon_interval); static ssize_t store_selfballoon_interval(struct device *dev, struct device_attribute *attr, const char *buf, size_t count) { unsigned long val; int err; if (!capable(CAP_SYS_ADMIN)) return -EPERM; err = kstrtoul(buf, 10, &val); if (err) return err; if (val == 0) return -EINVAL; selfballoon_interval = val; return count; } static DEVICE_ATTR(selfballoon_interval, S_IRUGO | S_IWUSR, show_selfballoon_interval, store_selfballoon_interval); SELFBALLOON_SHOW(selfballoon_downhys, "%d\n", selfballoon_downhysteresis); static ssize_t store_selfballoon_downhys(struct device *dev, struct device_attribute *attr, const char *buf, size_t count) { unsigned long val; int err; if (!capable(CAP_SYS_ADMIN)) return -EPERM; err = kstrtoul(buf, 10, &val); if (err) return err; if (val == 0) return -EINVAL; selfballoon_downhysteresis = val; return count; } static DEVICE_ATTR(selfballoon_downhysteresis, S_IRUGO | S_IWUSR, show_selfballoon_downhys, store_selfballoon_downhys); SELFBALLOON_SHOW(selfballoon_uphys, "%d\n", selfballoon_uphysteresis); static ssize_t store_selfballoon_uphys(struct device *dev, struct device_attribute *attr, const char *buf, size_t count) { unsigned long val; int err; if (!capable(CAP_SYS_ADMIN)) return -EPERM; err = kstrtoul(buf, 10, &val); if (err) return err; if (val == 0) return -EINVAL; selfballoon_uphysteresis = val; return count; } static DEVICE_ATTR(selfballoon_uphysteresis, S_IRUGO | S_IWUSR, show_selfballoon_uphys, store_selfballoon_uphys); SELFBALLOON_SHOW(selfballoon_min_usable_mb, "%d\n", selfballoon_min_usable_mb); static ssize_t store_selfballoon_min_usable_mb(struct device *dev, struct device_attribute *attr, const char *buf, size_t count) { unsigned long val; int err; if (!capable(CAP_SYS_ADMIN)) return -EPERM; err = kstrtoul(buf, 10, &val); if (err) return err; if (val == 0) return -EINVAL; selfballoon_min_usable_mb = val; return count; } static DEVICE_ATTR(selfballoon_min_usable_mb, S_IRUGO | S_IWUSR, show_selfballoon_min_usable_mb, store_selfballoon_min_usable_mb); SELFBALLOON_SHOW(selfballoon_reserved_mb, "%d\n", selfballoon_reserved_mb); static ssize_t store_selfballoon_reserved_mb(struct device *dev, struct device_attribute *attr, const char *buf, size_t count) { unsigned long val; int err; if (!capable(CAP_SYS_ADMIN)) return -EPERM; err = kstrtoul(buf, 10, &val); if (err) return err; if (val == 0) return -EINVAL; selfballoon_reserved_mb = val; return count; } static DEVICE_ATTR(selfballoon_reserved_mb, S_IRUGO | S_IWUSR, show_selfballoon_reserved_mb, store_selfballoon_reserved_mb); #ifdef CONFIG_FRONTSWAP SELFBALLOON_SHOW(frontswap_selfshrinking, "%d\n", frontswap_selfshrinking); static ssize_t store_frontswap_selfshrinking(struct device *dev, struct device_attribute *attr, const char *buf, size_t count) { bool was_enabled = frontswap_selfshrinking; unsigned long tmp; int err; if (!capable(CAP_SYS_ADMIN)) return -EPERM; err = kstrtoul(buf, 10, &tmp); if (err) return err; if ((tmp != 0) && (tmp != 1)) return -EINVAL; frontswap_selfshrinking = !!tmp; if (!was_enabled && !xen_selfballooning_enabled && frontswap_selfshrinking) schedule_delayed_work(&selfballoon_worker, selfballoon_interval * HZ); return count; } static DEVICE_ATTR(frontswap_selfshrinking, S_IRUGO | S_IWUSR, show_frontswap_selfshrinking, store_frontswap_selfshrinking); SELFBALLOON_SHOW(frontswap_inertia, "%d\n", frontswap_inertia); static ssize_t store_frontswap_inertia(struct device *dev, struct device_attribute *attr, const char *buf, size_t count) { unsigned long val; int err; if (!capable(CAP_SYS_ADMIN)) return -EPERM; err = kstrtoul(buf, 10, &val); if (err) return err; if (val == 0) return -EINVAL; frontswap_inertia = val; frontswap_inertia_counter = val; return count; } static DEVICE_ATTR(frontswap_inertia, S_IRUGO | S_IWUSR, show_frontswap_inertia, store_frontswap_inertia); SELFBALLOON_SHOW(frontswap_hysteresis, "%d\n", frontswap_hysteresis); static ssize_t store_frontswap_hysteresis(struct device *dev, struct device_attribute *attr, const char *buf, size_t count) { unsigned long val; int err; if (!capable(CAP_SYS_ADMIN)) return -EPERM; err = kstrtoul(buf, 10, &val); if (err) return err; if (val == 0) return -EINVAL; frontswap_hysteresis = val; return count; } static DEVICE_ATTR(frontswap_hysteresis, S_IRUGO | S_IWUSR, show_frontswap_hysteresis, store_frontswap_hysteresis); #endif /* CONFIG_FRONTSWAP */ static struct attribute *selfballoon_attrs[] = { &dev_attr_selfballooning.attr, &dev_attr_selfballoon_interval.attr, &dev_attr_selfballoon_downhysteresis.attr, &dev_attr_selfballoon_uphysteresis.attr, &dev_attr_selfballoon_min_usable_mb.attr, &dev_attr_selfballoon_reserved_mb.attr, #ifdef CONFIG_FRONTSWAP &dev_attr_frontswap_selfshrinking.attr, &dev_attr_frontswap_hysteresis.attr, &dev_attr_frontswap_inertia.attr, #endif NULL }; static const struct attribute_group selfballoon_group = { .name = "selfballoon", .attrs = selfballoon_attrs }; #endif int register_xen_selfballooning(struct device *dev) { int error = -1; #ifdef CONFIG_SYSFS error = sysfs_create_group(&dev->kobj, &selfballoon_group); #endif return error; } EXPORT_SYMBOL(register_xen_selfballooning); int xen_selfballoon_init(bool use_selfballooning, bool use_frontswap_selfshrink) { bool enable = false; unsigned long reserve_pages; if (!xen_domain()) return -ENODEV; if (xen_initial_domain()) { pr_info("Xen selfballooning driver disabled for domain0\n"); return -ENODEV; } xen_selfballooning_enabled = tmem_enabled && use_selfballooning; if (xen_selfballooning_enabled) { pr_info("Initializing Xen selfballooning driver\n"); enable = true; } #ifdef CONFIG_FRONTSWAP frontswap_selfshrinking = tmem_enabled && use_frontswap_selfshrink; if (frontswap_selfshrinking) { pr_info("Initializing frontswap selfshrinking driver\n"); enable = true; } #endif if (!enable) return -ENODEV; /* * Give selfballoon_reserved_mb a default value(10% of total ram pages) * to make selfballoon not so aggressive. * * There are mainly two reasons: * 1) The original goal_page didn't consider some pages used by kernel * space, like slab pages and memory used by device drivers. * * 2) The balloon driver may not give back memory to guest OS fast * enough when the workload suddenly aquries a lot of physical memory. * * In both cases, the guest OS will suffer from memory pressure and * OOM killer may be triggered. * By reserving extra 10% of total ram pages, we can keep the system * much more reliably and response faster in some cases. */ if (!selfballoon_reserved_mb) { reserve_pages = totalram_pages() / 10; selfballoon_reserved_mb = PAGES2MB(reserve_pages); } schedule_delayed_work(&selfballoon_worker, selfballoon_interval * HZ); return 0; } EXPORT_SYMBOL(xen_selfballoon_init);
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