[linux.git] / drivers / xen / xen-selfballoon.c

// 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/bootmem.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);
Commit	Line	Data
b2441318	1	// SPDX-License-Identifier: GPL-2.0
a50777c7 DM	2	/******************************************************************************
	3	* Xen selfballoon driver (and optional frontswap self-shrinking driver)
	4	*
	5	* Copyright (c) 2009-2011, Dan Magenheimer, Oracle Corp.
	6	*
	7	* This code complements the cleancache and frontswap patchsets to optimize
	8	* support for Xen Transcendent Memory ("tmem"). The policy it implements
	9	* is rudimentary and will likely improve over time, but it does work well
	10	* enough today.
	11	*
	12	* Two functionalities are implemented here which both use "control theory"
	13	* (feedback) to optimize memory utilization. In a virtualized environment
	14	* such as Xen, RAM is often a scarce resource and we would like to ensure
	15	* that each of a possibly large number of virtual machines is using RAM
	16	* efficiently, i.e. using as little as possible when under light load
	17	* and obtaining as much as possible when memory demands are high.
	18	* Since RAM needs vary highly dynamically and sometimes dramatically,
	19	* "hysteresis" is used, that is, memory target is determined not just
	20	* on current data but also on past data stored in the system.
	21	*
	22	* "Selfballooning" creates memory pressure by managing the Xen balloon
	23	* driver to decrease and increase available kernel memory, driven
	24	* largely by the target value of "Committed_AS" (see /proc/meminfo).
	25	* Since Committed_AS does not account for clean mapped pages (i.e. pages
	26	* in RAM that are identical to pages on disk), selfballooning has the
	27	* affect of pushing less frequently used clean pagecache pages out of
	28	* kernel RAM and, presumably using cleancache, into Xen tmem where
	29	* Xen can more efficiently optimize RAM utilization for such pages.
	30	*
	31	* When kernel memory demand unexpectedly increases faster than Xen, via
	32	* the selfballoon driver, is able to (or chooses to) provide usable RAM,
	33	* the kernel may invoke swapping. In most cases, frontswap is able
	34	* to absorb this swapping into Xen tmem. However, due to the fact
	35	* that the kernel swap subsystem assumes swapping occurs to a disk,
	36	* swapped pages may sit on the disk for a very long time; even if
	37	* the kernel knows the page will never be used again. This is because
	38	* the disk space costs very little and can be overwritten when
	39	* necessary. When such stale pages are in frontswap, however, they
	40	* are taking up valuable real estate. "Frontswap selfshrinking" works
	41	* to resolve this: When frontswap activity is otherwise stable
	42	* and the guest kernel is not under memory pressure, the "frontswap
	43	* selfshrinking" accounts for this by providing pressure to remove some
	44	* pages from frontswap and return them to kernel memory.
	45	*
	46	* For both "selfballooning" and "frontswap-selfshrinking", a worker
	47	* thread is used and sysfs tunables are provided to adjust the frequency
	48	* and rate of adjustments to achieve the goal, as well as to disable one
	49	* or both functions independently.
	50	*
	51	* While some argue that this functionality can and should be implemented
	52	* in userspace, it has been observed that bad things happen (e.g. OOMs).
	53	*
	54	* System configuration note: Selfballooning should not be enabled on
	55	* systems without a sufficiently large swap device configured; for best
	56	* results, it is recommended that total swap be increased by the size
37d46e15 KRW	57	* of the guest memory. Note, that selfballooning should be disabled by default
	58	* if frontswap is not configured. Similarly selfballooning should be enabled
	59	* by default if frontswap is configured and can be disabled with the
	60	* "tmem.selfballooning=0" kernel boot option. Finally, when frontswap is
	61	* configured, frontswap-selfshrinking can be disabled with the
	62	* "tmem.selfshrink=0" kernel boot option.
a50777c7 DM	63	*
	64	* Selfballooning is disallowed in domain0 and force-disabled.
	65	*
	66	*/
	67
283c0972 JP	68	#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
283c0972 JP	69
a50777c7	70	#include <linux/kernel.h>
38a1ed4f DM	71	#include <linux/bootmem.h>
38a1ed4f DM	72	#include <linux/swap.h>
a50777c7 DM	73	#include <linux/mm.h>
a50777c7 DM	74	#include <linux/mman.h>
0642d2ed	75	#include <linux/workqueue.h>
cb0c05c5	76	#include <linux/device.h>
a50777c7	77	#include <xen/balloon.h>
a50777c7	78	#include <xen/tmem.h>
0642d2ed	79	#include <xen/xen.h>
a50777c7 DM	80
	81	/* Enable/disable with sysfs. */
	82	static int xen_selfballooning_enabled __read_mostly;
	83
	84	/*
	85	* Controls rate at which memory target (this iteration) approaches
	86	* ultimate goal when memory need is increasing (up-hysteresis) or
	87	* decreasing (down-hysteresis). Higher values of hysteresis cause
	88	* slower increases/decreases. The default values for the various
	89	* parameters were deemed reasonable by experimentation, may be
	90	* workload-dependent, and can all be adjusted via sysfs.
	91	*/
	92	static unsigned int selfballoon_downhysteresis __read_mostly = 8;
	93	static unsigned int selfballoon_uphysteresis __read_mostly = 1;
	94
	95	/* In HZ, controls frequency of worker invocation. */
	96	static unsigned int selfballoon_interval __read_mostly = 5;
	97
38a1ed4f DM	98	/*
	99	* Minimum usable RAM in MB for selfballooning target for balloon.
	100	* If non-zero, it is added to totalreserve_pages and self-ballooning
	101	* will not balloon below the sum. If zero, a piecewise linear function
	102	* is calculated as a minimum and added to totalreserve_pages. Note that
	103	* setting this value indiscriminately may cause OOMs and crashes.
	104	*/
	105	static unsigned int selfballoon_min_usable_mb;
	106
d79d5959 JS	107	/*
	108	* Amount of RAM in MB to add to the target number of pages.
	109	* Can be used to reserve some more room for caches and the like.
	110	*/
	111	static unsigned int selfballoon_reserved_mb;
	112
a50777c7 DM	113	static void selfballoon_process(struct work_struct *work);
	114	static DECLARE_DELAYED_WORK(selfballoon_worker, selfballoon_process);
	115
	116	#ifdef CONFIG_FRONTSWAP
	117	#include <linux/frontswap.h>
	118
	119	/* Enable/disable with sysfs. */
	120	static bool frontswap_selfshrinking __read_mostly;
	121
a50777c7 DM	122	/*
	123	* The default values for the following parameters were deemed reasonable
	124	* by experimentation, may be workload-dependent, and can all be
	125	* adjusted via sysfs.
	126	*/
	127
	128	/* Control rate for frontswap shrinking. Higher hysteresis is slower. */
	129	static unsigned int frontswap_hysteresis __read_mostly = 20;
	130
	131	/*
	132	* Number of selfballoon worker invocations to wait before observing that
	133	* frontswap selfshrinking should commence. Note that selfshrinking does
	134	* not use a separate worker thread.
	135	*/
	136	static unsigned int frontswap_inertia __read_mostly = 3;
	137
	138	/* Countdown to next invocation of frontswap_shrink() */
	139	static unsigned long frontswap_inertia_counter;
	140
	141	/*
	142	* Invoked by the selfballoon worker thread, uses current number of pages
	143	* in frontswap (frontswap_curr_pages()), previous status, and control
	144	* values (hysteresis and inertia) to determine if frontswap should be
	145	* shrunk and what the new frontswap size should be. Note that
	146	* frontswap_shrink is essentially a partial swapoff that immediately
	147	* transfers pages from the "swap device" (frontswap) back into kernel
	148	* RAM; despite the name, frontswap "shrinking" is very different from
	149	* the "shrinker" interface used by the kernel MM subsystem to reclaim
	150	* memory.
	151	*/
	152	static void frontswap_selfshrink(void)
	153	{
	154	static unsigned long cur_frontswap_pages;
03993730 GS	155	unsigned long last_frontswap_pages;
03993730 GS	156	unsigned long tgt_frontswap_pages;
a50777c7 DM	157
	158	last_frontswap_pages = cur_frontswap_pages;
	159	cur_frontswap_pages = frontswap_curr_pages();
	160	if (!cur_frontswap_pages \|\|
	161	(cur_frontswap_pages > last_frontswap_pages)) {
	162	frontswap_inertia_counter = frontswap_inertia;
	163	return;
	164	}
	165	if (frontswap_inertia_counter && --frontswap_inertia_counter)
	166	return;
	167	if (cur_frontswap_pages <= frontswap_hysteresis)
	168	tgt_frontswap_pages = 0;
	169	else
	170	tgt_frontswap_pages = cur_frontswap_pages -
	171	(cur_frontswap_pages / frontswap_hysteresis);
	172	frontswap_shrink(tgt_frontswap_pages);
d4c7abdf	173	frontswap_inertia_counter = frontswap_inertia;
a50777c7 DM	174	}
a50777c7 DM	175
a50777c7 DM	176	#endif /* CONFIG_FRONTSWAP */
a50777c7 DM	177
38a1ed4f	178	#define MB2PAGES(mb) ((mb) << (20 - PAGE_SHIFT))
bc1b0df5	179	#define PAGES2MB(pages) ((pages) >> (20 - PAGE_SHIFT))
38a1ed4f	180
a50777c7 DM	181	/*
	182	* Use current balloon size, the goal (vm_committed_as), and hysteresis
	183	* parameters to set a new target balloon size
	184	*/
	185	static void selfballoon_process(struct work_struct *work)
	186	{
38a1ed4f DM	187	unsigned long cur_pages, goal_pages, tgt_pages, floor_pages;
38a1ed4f DM	188	unsigned long useful_pages;
a50777c7 DM	189	bool reset_timer = false;
	190
	191	if (xen_selfballooning_enabled) {
38a1ed4f	192	cur_pages = totalram_pages;
a50777c7	193	tgt_pages = cur_pages; /* default is no change */
997071bc	194	goal_pages = vm_memory_committed() +
d79d5959 JS	195	totalreserve_pages +
d79d5959 JS	196	MB2PAGES(selfballoon_reserved_mb);
a50777c7 DM	197	#ifdef CONFIG_FRONTSWAP
a50777c7 DM	198	/* allow space for frontswap pages to be repatriated */
8ea1d2a1	199	if (frontswap_selfshrinking)
a50777c7 DM	200	goal_pages += frontswap_curr_pages();
	201	#endif
	202	if (cur_pages > goal_pages)
	203	tgt_pages = cur_pages -
	204	((cur_pages - goal_pages) /
	205	selfballoon_downhysteresis);
	206	else if (cur_pages < goal_pages)
	207	tgt_pages = cur_pages +
	208	((goal_pages - cur_pages) /
	209	selfballoon_uphysteresis);
	210	/* else if cur_pages == goal_pages, no change */
38a1ed4f DM	211	useful_pages = max_pfn - totalreserve_pages;
	212	if (selfballoon_min_usable_mb != 0)
	213	floor_pages = totalreserve_pages +
	214	MB2PAGES(selfballoon_min_usable_mb);
	215	/* piecewise linear function ending in ~3% slope */
	216	else if (useful_pages < MB2PAGES(16))
	217	floor_pages = max_pfn; /* not worth ballooning */
	218	else if (useful_pages < MB2PAGES(64))
	219	floor_pages = totalreserve_pages + MB2PAGES(16) +
	220	((useful_pages - MB2PAGES(16)) >> 1);
	221	else if (useful_pages < MB2PAGES(512))
	222	floor_pages = totalreserve_pages + MB2PAGES(40) +
	223	((useful_pages - MB2PAGES(40)) >> 3);
	224	else /* useful_pages >= MB2PAGES(512) */
	225	floor_pages = totalreserve_pages + MB2PAGES(99) +
	226	((useful_pages - MB2PAGES(99)) >> 5);
	227	if (tgt_pages < floor_pages)
	228	tgt_pages = floor_pages;
	229	balloon_set_new_target(tgt_pages +
	230	balloon_stats.current_pages - totalram_pages);
a50777c7 DM	231	reset_timer = true;
	232	}
	233	#ifdef CONFIG_FRONTSWAP
8ea1d2a1	234	if (frontswap_selfshrinking) {
a50777c7 DM	235	frontswap_selfshrink();
	236	reset_timer = true;
	237	}
	238	#endif
	239	if (reset_timer)
	240	schedule_delayed_work(&selfballoon_worker,
	241	selfballoon_interval * HZ);
	242	}
	243
	244	#ifdef CONFIG_SYSFS
	245
a50777c7 DM	246	#include <linux/capability.h>
	247
	248	#define SELFBALLOON_SHOW(name, format, args...) \
07068021 KS	249	static ssize_t show_##name(struct device *dev, \
	250	struct device_attribute *attr, \
	251	char *buf) \
a50777c7 DM	252	{ \
	253	return sprintf(buf, format, ##args); \
	254	}
	255
	256	SELFBALLOON_SHOW(selfballooning, "%d\n", xen_selfballooning_enabled);
	257
07068021 KS	258	static ssize_t store_selfballooning(struct device *dev,
07068021 KS	259	struct device_attribute *attr,
a50777c7 DM	260	const char *buf,
	261	size_t count)
	262	{
	263	bool was_enabled = xen_selfballooning_enabled;
	264	unsigned long tmp;
	265	int err;
	266
	267	if (!capable(CAP_SYS_ADMIN))
	268	return -EPERM;
	269
d3dbd93d JH	270	err = kstrtoul(buf, 10, &tmp);
	271	if (err)
	272	return err;
	273	if ((tmp != 0) && (tmp != 1))
a50777c7 DM	274	return -EINVAL;
	275
	276	xen_selfballooning_enabled = !!tmp;
	277	if (!was_enabled && xen_selfballooning_enabled)
	278	schedule_delayed_work(&selfballoon_worker,
	279	selfballoon_interval * HZ);
	280
	281	return count;
	282	}
	283
07068021	284	static DEVICE_ATTR(selfballooning, S_IRUGO \| S_IWUSR,
a50777c7 DM	285	show_selfballooning, store_selfballooning);
	286
	287	SELFBALLOON_SHOW(selfballoon_interval, "%d\n", selfballoon_interval);
	288
07068021 KS	289	static ssize_t store_selfballoon_interval(struct device *dev,
07068021 KS	290	struct device_attribute *attr,
a50777c7 DM	291	const char *buf,
	292	size_t count)
	293	{
	294	unsigned long val;
	295	int err;
	296
	297	if (!capable(CAP_SYS_ADMIN))
	298	return -EPERM;
d3dbd93d JH	299	err = kstrtoul(buf, 10, &val);
	300	if (err)
	301	return err;
	302	if (val == 0)
a50777c7 DM	303	return -EINVAL;
	304	selfballoon_interval = val;
	305	return count;
	306	}
	307
07068021	308	static DEVICE_ATTR(selfballoon_interval, S_IRUGO \| S_IWUSR,
a50777c7 DM	309	show_selfballoon_interval, store_selfballoon_interval);
	310
	311	SELFBALLOON_SHOW(selfballoon_downhys, "%d\n", selfballoon_downhysteresis);
	312
07068021 KS	313	static ssize_t store_selfballoon_downhys(struct device *dev,
07068021 KS	314	struct device_attribute *attr,
a50777c7 DM	315	const char *buf,
	316	size_t count)
	317	{
	318	unsigned long val;
	319	int err;
	320
	321	if (!capable(CAP_SYS_ADMIN))
	322	return -EPERM;
d3dbd93d JH	323	err = kstrtoul(buf, 10, &val);
	324	if (err)
	325	return err;
	326	if (val == 0)
a50777c7 DM	327	return -EINVAL;
	328	selfballoon_downhysteresis = val;
	329	return count;
	330	}
	331
07068021	332	static DEVICE_ATTR(selfballoon_downhysteresis, S_IRUGO \| S_IWUSR,
a50777c7 DM	333	show_selfballoon_downhys, store_selfballoon_downhys);
	334
	335
	336	SELFBALLOON_SHOW(selfballoon_uphys, "%d\n", selfballoon_uphysteresis);
	337
07068021 KS	338	static ssize_t store_selfballoon_uphys(struct device *dev,
07068021 KS	339	struct device_attribute *attr,
a50777c7 DM	340	const char *buf,
	341	size_t count)
	342	{
	343	unsigned long val;
	344	int err;
	345
	346	if (!capable(CAP_SYS_ADMIN))
	347	return -EPERM;
d3dbd93d JH	348	err = kstrtoul(buf, 10, &val);
	349	if (err)
	350	return err;
	351	if (val == 0)
a50777c7 DM	352	return -EINVAL;
	353	selfballoon_uphysteresis = val;
	354	return count;
	355	}
	356
07068021	357	static DEVICE_ATTR(selfballoon_uphysteresis, S_IRUGO \| S_IWUSR,
a50777c7 DM	358	show_selfballoon_uphys, store_selfballoon_uphys);
a50777c7 DM	359
38a1ed4f DM	360	SELFBALLOON_SHOW(selfballoon_min_usable_mb, "%d\n",
	361	selfballoon_min_usable_mb);
	362
07068021 KS	363	static ssize_t store_selfballoon_min_usable_mb(struct device *dev,
07068021 KS	364	struct device_attribute *attr,
38a1ed4f DM	365	const char *buf,
	366	size_t count)
	367	{
	368	unsigned long val;
	369	int err;
	370
	371	if (!capable(CAP_SYS_ADMIN))
	372	return -EPERM;
d3dbd93d JH	373	err = kstrtoul(buf, 10, &val);
	374	if (err)
	375	return err;
	376	if (val == 0)
38a1ed4f DM	377	return -EINVAL;
	378	selfballoon_min_usable_mb = val;
	379	return count;
	380	}
	381
07068021	382	static DEVICE_ATTR(selfballoon_min_usable_mb, S_IRUGO \| S_IWUSR,
38a1ed4f DM	383	show_selfballoon_min_usable_mb,
	384	store_selfballoon_min_usable_mb);
	385
d79d5959 JS	386	SELFBALLOON_SHOW(selfballoon_reserved_mb, "%d\n",
	387	selfballoon_reserved_mb);
	388
	389	static ssize_t store_selfballoon_reserved_mb(struct device *dev,
	390	struct device_attribute *attr,
	391	const char *buf,
	392	size_t count)
	393	{
	394	unsigned long val;
	395	int err;
	396
	397	if (!capable(CAP_SYS_ADMIN))
	398	return -EPERM;
d3dbd93d JH	399	err = kstrtoul(buf, 10, &val);
	400	if (err)
	401	return err;
	402	if (val == 0)
d79d5959 JS	403	return -EINVAL;
	404	selfballoon_reserved_mb = val;
	405	return count;
	406	}
	407
	408	static DEVICE_ATTR(selfballoon_reserved_mb, S_IRUGO \| S_IWUSR,
	409	show_selfballoon_reserved_mb,
	410	store_selfballoon_reserved_mb);
	411
38a1ed4f	412
a50777c7 DM	413	#ifdef CONFIG_FRONTSWAP
	414	SELFBALLOON_SHOW(frontswap_selfshrinking, "%d\n", frontswap_selfshrinking);
	415
07068021 KS	416	static ssize_t store_frontswap_selfshrinking(struct device *dev,
07068021 KS	417	struct device_attribute *attr,
a50777c7 DM	418	const char *buf,
	419	size_t count)
	420	{
	421	bool was_enabled = frontswap_selfshrinking;
	422	unsigned long tmp;
	423	int err;
	424
	425	if (!capable(CAP_SYS_ADMIN))
	426	return -EPERM;
d3dbd93d JH	427	err = kstrtoul(buf, 10, &tmp);
	428	if (err)
	429	return err;
	430	if ((tmp != 0) && (tmp != 1))
a50777c7 DM	431	return -EINVAL;
	432	frontswap_selfshrinking = !!tmp;
	433	if (!was_enabled && !xen_selfballooning_enabled &&
	434	frontswap_selfshrinking)
	435	schedule_delayed_work(&selfballoon_worker,
	436	selfballoon_interval * HZ);
	437
	438	return count;
	439	}
	440
07068021	441	static DEVICE_ATTR(frontswap_selfshrinking, S_IRUGO \| S_IWUSR,
a50777c7 DM	442	show_frontswap_selfshrinking, store_frontswap_selfshrinking);
	443
	444	SELFBALLOON_SHOW(frontswap_inertia, "%d\n", frontswap_inertia);
	445
07068021 KS	446	static ssize_t store_frontswap_inertia(struct device *dev,
07068021 KS	447	struct device_attribute *attr,
a50777c7 DM	448	const char *buf,
	449	size_t count)
	450	{
	451	unsigned long val;
	452	int err;
	453
	454	if (!capable(CAP_SYS_ADMIN))
	455	return -EPERM;
d3dbd93d JH	456	err = kstrtoul(buf, 10, &val);
	457	if (err)
	458	return err;
	459	if (val == 0)
a50777c7 DM	460	return -EINVAL;
	461	frontswap_inertia = val;
	462	frontswap_inertia_counter = val;
	463	return count;
	464	}
	465
07068021	466	static DEVICE_ATTR(frontswap_inertia, S_IRUGO \| S_IWUSR,
a50777c7 DM	467	show_frontswap_inertia, store_frontswap_inertia);
	468
	469	SELFBALLOON_SHOW(frontswap_hysteresis, "%d\n", frontswap_hysteresis);
	470
07068021 KS	471	static ssize_t store_frontswap_hysteresis(struct device *dev,
07068021 KS	472	struct device_attribute *attr,
a50777c7 DM	473	const char *buf,
	474	size_t count)
	475	{
	476	unsigned long val;
	477	int err;
	478
	479	if (!capable(CAP_SYS_ADMIN))
	480	return -EPERM;
d3dbd93d JH	481	err = kstrtoul(buf, 10, &val);
	482	if (err)
	483	return err;
	484	if (val == 0)
a50777c7 DM	485	return -EINVAL;
	486	frontswap_hysteresis = val;
	487	return count;
	488	}
	489
07068021	490	static DEVICE_ATTR(frontswap_hysteresis, S_IRUGO \| S_IWUSR,
a50777c7 DM	491	show_frontswap_hysteresis, store_frontswap_hysteresis);
	492
	493	#endif /* CONFIG_FRONTSWAP */
	494
	495	static struct attribute *selfballoon_attrs[] = {
07068021 KS	496	&dev_attr_selfballooning.attr,
	497	&dev_attr_selfballoon_interval.attr,
	498	&dev_attr_selfballoon_downhysteresis.attr,
	499	&dev_attr_selfballoon_uphysteresis.attr,
	500	&dev_attr_selfballoon_min_usable_mb.attr,
d79d5959	501	&dev_attr_selfballoon_reserved_mb.attr,
a50777c7	502	#ifdef CONFIG_FRONTSWAP
07068021 KS	503	&dev_attr_frontswap_selfshrinking.attr,
	504	&dev_attr_frontswap_hysteresis.attr,
	505	&dev_attr_frontswap_inertia.attr,
a50777c7 DM	506	#endif
	507	NULL
	508	};
	509
ead1d014	510	static const struct attribute_group selfballoon_group = {
a50777c7 DM	511	.name = "selfballoon",
	512	.attrs = selfballoon_attrs
	513	};
	514	#endif
	515
07068021	516	int register_xen_selfballooning(struct device *dev)
a50777c7 DM	517	{
	518	int error = -1;
	519
	520	#ifdef CONFIG_SYSFS
07068021	521	error = sysfs_create_group(&dev->kobj, &selfballoon_group);
a50777c7 DM	522	#endif
	523	return error;
	524	}
	525	EXPORT_SYMBOL(register_xen_selfballooning);
	526
10a7a077	527	int xen_selfballoon_init(bool use_selfballooning, bool use_frontswap_selfshrink)
a50777c7 DM	528	{
a50777c7 DM	529	bool enable = false;
bc1b0df5	530	unsigned long reserve_pages;
a50777c7 DM	531
	532	if (!xen_domain())
	533	return -ENODEV;
	534
	535	if (xen_initial_domain()) {
283c0972	536	pr_info("Xen selfballooning driver disabled for domain0\n");
a50777c7 DM	537	return -ENODEV;
	538	}
	539
	540	xen_selfballooning_enabled = tmem_enabled && use_selfballooning;
	541	if (xen_selfballooning_enabled) {
283c0972	542	pr_info("Initializing Xen selfballooning driver\n");
a50777c7 DM	543	enable = true;
	544	}
	545	#ifdef CONFIG_FRONTSWAP
	546	frontswap_selfshrinking = tmem_enabled && use_frontswap_selfshrink;
	547	if (frontswap_selfshrinking) {
283c0972	548	pr_info("Initializing frontswap selfshrinking driver\n");
a50777c7 DM	549	enable = true;
	550	}
	551	#endif
	552	if (!enable)
	553	return -ENODEV;
	554
bc1b0df5 BL	555	/*
	556	* Give selfballoon_reserved_mb a default value(10% of total ram pages)
	557	* to make selfballoon not so aggressive.
	558	*
	559	* There are mainly two reasons:
	560	* 1) The original goal_page didn't consider some pages used by kernel
	561	* space, like slab pages and memory used by device drivers.
	562	*
	563	* 2) The balloon driver may not give back memory to guest OS fast
	564	* enough when the workload suddenly aquries a lot of physical memory.
	565	*
	566	* In both cases, the guest OS will suffer from memory pressure and
	567	* OOM killer may be triggered.
	568	* By reserving extra 10% of total ram pages, we can keep the system
	569	* much more reliably and response faster in some cases.
	570	*/
	571	if (!selfballoon_reserved_mb) {
	572	reserve_pages = totalram_pages / 10;
	573	selfballoon_reserved_mb = PAGES2MB(reserve_pages);
	574	}
a50777c7 DM	575	schedule_delayed_work(&selfballoon_worker, selfballoon_interval * HZ);
	576
	577	return 0;
	578	}
10a7a077	579	EXPORT_SYMBOL(xen_selfballoon_init);