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-rw-r--r--drivers/xen/xen-selfballoon.c579
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diff --git a/drivers/xen/xen-selfballoon.c b/drivers/xen/xen-selfballoon.c
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-// 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);