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Diffstat (limited to 'drivers/xen/xen-selfballoon.c')
| -rw-r--r-- | drivers/xen/xen-selfballoon.c | 579 |
1 files changed, 0 insertions, 579 deletions
diff --git a/drivers/xen/xen-selfballoon.c b/drivers/xen/xen-selfballoon.c deleted file mode 100644 index 246f6122c9ee..000000000000 --- a/drivers/xen/xen-selfballoon.c +++ /dev/null @@ -1,579 +0,0 @@ -// 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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