[mirror_ubuntu-bionic-kernel.git] / drivers / xen / xen-selfballoon.c

/******************************************************************************
 * 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.  Also, while technically not required to be
 * configured, it is highly recommended that frontswap also be configured
 * and enabled when selfballooning is running.  So, selfballooning
 * is disabled by default if frontswap is not configured and can only
 * be enabled with the "selfballooning" kernel boot option; similarly
 * selfballooning is enabled by default if frontswap is configured and
 * can be disabled with the "noselfballooning" kernel boot option.  Finally,
 * when frontswap is configured, frontswap-selfshrinking can be disabled
 * with the "noselfshrink" kernel boot option.
 *
 * Selfballooning is disallowed in domain0 and force-disabled.
 *
 */

#include <linux/kernel.h>
#include <linux/bootmem.h>
#include <linux/swap.h>
#include <linux/mm.h>
#include <linux/mman.h>
#include <linux/module.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;

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;

/* Enable/disable with kernel boot option. */
static bool use_frontswap_selfshrink __initdata = true;

/*
 * 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;
	static unsigned long last_frontswap_pages;
	static 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);
}

static int __init xen_nofrontswap_selfshrink_setup(char *s)
{
	use_frontswap_selfshrink = false;
	return 1;
}

__setup("noselfshrink", xen_nofrontswap_selfshrink_setup);

/* Disable with kernel boot option. */
static bool use_selfballooning __initdata = true;

static int __init xen_noselfballooning_setup(char *s)
{
	use_selfballooning = false;
	return 1;
}

__setup("noselfballooning", xen_noselfballooning_setup);
#else /* !CONFIG_FRONTSWAP */
/* Enable with kernel boot option. */
static bool use_selfballooning __initdata = false;

static int __init xen_selfballooning_setup(char *s)
{
	use_selfballooning = true;
	return 1;
}

__setup("selfballooning", xen_selfballooning_setup);
#endif /* CONFIG_FRONTSWAP */

#define MB2PAGES(mb)	((mb) << (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 = percpu_counter_read_positive(&vm_committed_as) +
				totalreserve_pages;
#ifdef CONFIG_FRONTSWAP
		/* allow space for frontswap pages to be repatriated */
		if (frontswap_selfshrinking && frontswap_enabled)
			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_enabled) {
		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 = strict_strtoul(buf, 10, &tmp);
	if (err || ((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 = strict_strtoul(buf, 10, &val);
	if (err || 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 = strict_strtoul(buf, 10, &val);
	if (err || 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 = strict_strtoul(buf, 10, &val);
	if (err || 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 = strict_strtoul(buf, 10, &val);
	if (err || 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);


#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 = strict_strtoul(buf, 10, &tmp);
	if (err || ((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 = strict_strtoul(buf, 10, &val);
	if (err || 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 = strict_strtoul(buf, 10, &val);
	if (err || 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,
#ifdef CONFIG_FRONTSWAP
	&dev_attr_frontswap_selfshrinking.attr,
	&dev_attr_frontswap_hysteresis.attr,
	&dev_attr_frontswap_inertia.attr,
#endif
	NULL
};

static 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);

static int __init xen_selfballoon_init(void)
{
	bool enable = false;

	if (!xen_domain())
		return -ENODEV;

	if (xen_initial_domain()) {
		pr_info("xen/balloon: Xen selfballooning driver "
				"disabled for domain0.\n");
		return -ENODEV;
	}

	xen_selfballooning_enabled = tmem_enabled && use_selfballooning;
	if (xen_selfballooning_enabled) {
		pr_info("xen/balloon: Initializing Xen "
					"selfballooning driver.\n");
		enable = true;
	}
#ifdef CONFIG_FRONTSWAP
	frontswap_selfshrinking = tmem_enabled && use_frontswap_selfshrink;
	if (frontswap_selfshrinking) {
		pr_info("xen/balloon: Initializing frontswap "
					"selfshrinking driver.\n");
		enable = true;
	}
#endif
	if (!enable)
		return -ENODEV;

	schedule_delayed_work(&selfballoon_worker, selfballoon_interval * HZ);

	return 0;
}

subsys_initcall(xen_selfballoon_init);

MODULE_LICENSE("GPL");
Commit	Line	Data
a50777c7 DM	1	/******************************************************************************
	2	* Xen selfballoon driver (and optional frontswap self-shrinking driver)
	3	*
	4	* Copyright (c) 2009-2011, Dan Magenheimer, Oracle Corp.
	5	*
	6	* This code complements the cleancache and frontswap patchsets to optimize
	7	* support for Xen Transcendent Memory ("tmem"). The policy it implements
	8	* is rudimentary and will likely improve over time, but it does work well
	9	* enough today.
	10	*
	11	* Two functionalities are implemented here which both use "control theory"
	12	* (feedback) to optimize memory utilization. In a virtualized environment
	13	* such as Xen, RAM is often a scarce resource and we would like to ensure
	14	* that each of a possibly large number of virtual machines is using RAM
	15	* efficiently, i.e. using as little as possible when under light load
	16	* and obtaining as much as possible when memory demands are high.
	17	* Since RAM needs vary highly dynamically and sometimes dramatically,
	18	* "hysteresis" is used, that is, memory target is determined not just
	19	* on current data but also on past data stored in the system.
	20	*
	21	* "Selfballooning" creates memory pressure by managing the Xen balloon
	22	* driver to decrease and increase available kernel memory, driven
	23	* largely by the target value of "Committed_AS" (see /proc/meminfo).
	24	* Since Committed_AS does not account for clean mapped pages (i.e. pages
	25	* in RAM that are identical to pages on disk), selfballooning has the
	26	* affect of pushing less frequently used clean pagecache pages out of
	27	* kernel RAM and, presumably using cleancache, into Xen tmem where
	28	* Xen can more efficiently optimize RAM utilization for such pages.
	29	*
	30	* When kernel memory demand unexpectedly increases faster than Xen, via
	31	* the selfballoon driver, is able to (or chooses to) provide usable RAM,
	32	* the kernel may invoke swapping. In most cases, frontswap is able
	33	* to absorb this swapping into Xen tmem. However, due to the fact
	34	* that the kernel swap subsystem assumes swapping occurs to a disk,
	35	* swapped pages may sit on the disk for a very long time; even if
	36	* the kernel knows the page will never be used again. This is because
	37	* the disk space costs very little and can be overwritten when
	38	* necessary. When such stale pages are in frontswap, however, they
	39	* are taking up valuable real estate. "Frontswap selfshrinking" works
	40	* to resolve this: When frontswap activity is otherwise stable
	41	* and the guest kernel is not under memory pressure, the "frontswap
	42	* selfshrinking" accounts for this by providing pressure to remove some
	43	* pages from frontswap and return them to kernel memory.
	44	*
	45	* For both "selfballooning" and "frontswap-selfshrinking", a worker
	46	* thread is used and sysfs tunables are provided to adjust the frequency
	47	* and rate of adjustments to achieve the goal, as well as to disable one
	48	* or both functions independently.
	49	*
	50	* While some argue that this functionality can and should be implemented
	51	* in userspace, it has been observed that bad things happen (e.g. OOMs).
	52	*
	53	* System configuration note: Selfballooning should not be enabled on
	54	* systems without a sufficiently large swap device configured; for best
	55	* results, it is recommended that total swap be increased by the size
	56	* of the guest memory. Also, while technically not required to be
	57	* configured, it is highly recommended that frontswap also be configured
	58	* and enabled when selfballooning is running. So, selfballooning
	59	* is disabled by default if frontswap is not configured and can only
	60	* be enabled with the "selfballooning" kernel boot option; similarly
	61	* selfballooning is enabled by default if frontswap is configured and
	62	* can be disabled with the "noselfballooning" kernel boot option. Finally,
	63	* when frontswap is configured, frontswap-selfshrinking can be disabled
	64	* with the "noselfshrink" kernel boot option.
65	*
66	* Selfballooning is disallowed in domain0 and force-disabled.
67	*
68	*/
69
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>
4fec0e0b	75	#include <linux/module.h>
0642d2ed	76	#include <linux/workqueue.h>
cb0c05c5	77	#include <linux/device.h>
a50777c7	78	#include <xen/balloon.h>
a50777c7	79	#include <xen/tmem.h>
0642d2ed	80	#include <xen/xen.h>
a50777c7 DM	81
	82	/* Enable/disable with sysfs. */
	83	static int xen_selfballooning_enabled __read_mostly;
	84
	85	/*
	86	* Controls rate at which memory target (this iteration) approaches
	87	* ultimate goal when memory need is increasing (up-hysteresis) or
	88	* decreasing (down-hysteresis). Higher values of hysteresis cause
	89	* slower increases/decreases. The default values for the various
	90	* parameters were deemed reasonable by experimentation, may be
	91	* workload-dependent, and can all be adjusted via sysfs.
	92	*/
	93	static unsigned int selfballoon_downhysteresis __read_mostly = 8;
	94	static unsigned int selfballoon_uphysteresis __read_mostly = 1;
	95
	96	/* In HZ, controls frequency of worker invocation. */
	97	static unsigned int selfballoon_interval __read_mostly = 5;
	98
38a1ed4f DM	99	/*
	100	* Minimum usable RAM in MB for selfballooning target for balloon.
	101	* If non-zero, it is added to totalreserve_pages and self-ballooning
	102	* will not balloon below the sum. If zero, a piecewise linear function
	103	* is calculated as a minimum and added to totalreserve_pages. Note that
	104	* setting this value indiscriminately may cause OOMs and crashes.
	105	*/
	106	static unsigned int selfballoon_min_usable_mb;
	107
a50777c7 DM	108	static void selfballoon_process(struct work_struct *work);
	109	static DECLARE_DELAYED_WORK(selfballoon_worker, selfballoon_process);
	110
	111	#ifdef CONFIG_FRONTSWAP
	112	#include <linux/frontswap.h>
	113
	114	/* Enable/disable with sysfs. */
	115	static bool frontswap_selfshrinking __read_mostly;
	116
	117	/* Enable/disable with kernel boot option. */
	118	static bool use_frontswap_selfshrink __initdata = true;
	119
	120	/*
	121	* The default values for the following parameters were deemed reasonable
	122	* by experimentation, may be workload-dependent, and can all be
	123	* adjusted via sysfs.
	124	*/
	125
	126	/* Control rate for frontswap shrinking. Higher hysteresis is slower. */
	127	static unsigned int frontswap_hysteresis __read_mostly = 20;
	128
	129	/*
	130	* Number of selfballoon worker invocations to wait before observing that
	131	* frontswap selfshrinking should commence. Note that selfshrinking does
	132	* not use a separate worker thread.
	133	*/
	134	static unsigned int frontswap_inertia __read_mostly = 3;
	135
	136	/* Countdown to next invocation of frontswap_shrink() */
	137	static unsigned long frontswap_inertia_counter;
	138
	139	/*
	140	* Invoked by the selfballoon worker thread, uses current number of pages
	141	* in frontswap (frontswap_curr_pages()), previous status, and control
	142	* values (hysteresis and inertia) to determine if frontswap should be
	143	* shrunk and what the new frontswap size should be. Note that
	144	* frontswap_shrink is essentially a partial swapoff that immediately
	145	* transfers pages from the "swap device" (frontswap) back into kernel
	146	* RAM; despite the name, frontswap "shrinking" is very different from
	147	* the "shrinker" interface used by the kernel MM subsystem to reclaim
	148	* memory.
	149	*/
	150	static void frontswap_selfshrink(void)
	151	{
	152	static unsigned long cur_frontswap_pages;
	153	static unsigned long last_frontswap_pages;
	154	static unsigned long tgt_frontswap_pages;
	155
	156	last_frontswap_pages = cur_frontswap_pages;
	157	cur_frontswap_pages = frontswap_curr_pages();
	158	if (!cur_frontswap_pages \|\|
	159	(cur_frontswap_pages > last_frontswap_pages)) {
	160	frontswap_inertia_counter = frontswap_inertia;
	161	return;
	162	}
	163	if (frontswap_inertia_counter && --frontswap_inertia_counter)
	164	return;
	165	if (cur_frontswap_pages <= frontswap_hysteresis)
	166	tgt_frontswap_pages = 0;
	167	else
	168	tgt_frontswap_pages = cur_frontswap_pages -
	169	(cur_frontswap_pages / frontswap_hysteresis);
	170	frontswap_shrink(tgt_frontswap_pages);
	171	}
172
173	static int __init xen_nofrontswap_selfshrink_setup(char *s)
174	{
175	use_frontswap_selfshrink = false;
176	return 1;
177	}
178
179	__setup("noselfshrink", xen_nofrontswap_selfshrink_setup);
180
181	/* Disable with kernel boot option. */
182	static bool use_selfballooning __initdata = true;
183
184	static int __init xen_noselfballooning_setup(char *s)
185	{
186	use_selfballooning = false;
187	return 1;
188	}
189
190	__setup("noselfballooning", xen_noselfballooning_setup);
191	#else /* !CONFIG_FRONTSWAP */
192	/* Enable with kernel boot option. */
193	static bool use_selfballooning __initdata = false;
194
195	static int __init xen_selfballooning_setup(char *s)
196	{
197	use_selfballooning = true;
198	return 1;
199	}
200
201	__setup("selfballooning", xen_selfballooning_setup);
202	#endif /* CONFIG_FRONTSWAP */
203
38a1ed4f DM	204	#define MB2PAGES(mb) ((mb) << (20 - PAGE_SHIFT))
38a1ed4f DM	205
a50777c7 DM	206	/*
	207	* Use current balloon size, the goal (vm_committed_as), and hysteresis
	208	* parameters to set a new target balloon size
	209	*/
	210	static void selfballoon_process(struct work_struct *work)
	211	{
38a1ed4f DM	212	unsigned long cur_pages, goal_pages, tgt_pages, floor_pages;
38a1ed4f DM	213	unsigned long useful_pages;
a50777c7 DM	214	bool reset_timer = false;
	215
	216	if (xen_selfballooning_enabled) {
38a1ed4f	217	cur_pages = totalram_pages;
a50777c7 DM	218	tgt_pages = cur_pages; /* default is no change */
a50777c7 DM	219	goal_pages = percpu_counter_read_positive(&vm_committed_as) +
38a1ed4f	220	totalreserve_pages;
a50777c7 DM	221	#ifdef CONFIG_FRONTSWAP
	222	/* allow space for frontswap pages to be repatriated */
	223	if (frontswap_selfshrinking && frontswap_enabled)
	224	goal_pages += frontswap_curr_pages();
	225	#endif
	226	if (cur_pages > goal_pages)
	227	tgt_pages = cur_pages -
	228	((cur_pages - goal_pages) /
	229	selfballoon_downhysteresis);
	230	else if (cur_pages < goal_pages)
	231	tgt_pages = cur_pages +
	232	((goal_pages - cur_pages) /
	233	selfballoon_uphysteresis);
	234	/* else if cur_pages == goal_pages, no change */
38a1ed4f DM	235	useful_pages = max_pfn - totalreserve_pages;
	236	if (selfballoon_min_usable_mb != 0)
	237	floor_pages = totalreserve_pages +
	238	MB2PAGES(selfballoon_min_usable_mb);
	239	/* piecewise linear function ending in ~3% slope */
	240	else if (useful_pages < MB2PAGES(16))
	241	floor_pages = max_pfn; /* not worth ballooning */
	242	else if (useful_pages < MB2PAGES(64))
	243	floor_pages = totalreserve_pages + MB2PAGES(16) +
	244	((useful_pages - MB2PAGES(16)) >> 1);
	245	else if (useful_pages < MB2PAGES(512))
	246	floor_pages = totalreserve_pages + MB2PAGES(40) +
	247	((useful_pages - MB2PAGES(40)) >> 3);
	248	else /* useful_pages >= MB2PAGES(512) */
	249	floor_pages = totalreserve_pages + MB2PAGES(99) +
	250	((useful_pages - MB2PAGES(99)) >> 5);
	251	if (tgt_pages < floor_pages)
	252	tgt_pages = floor_pages;
	253	balloon_set_new_target(tgt_pages +
	254	balloon_stats.current_pages - totalram_pages);
a50777c7 DM	255	reset_timer = true;
	256	}
	257	#ifdef CONFIG_FRONTSWAP
	258	if (frontswap_selfshrinking && frontswap_enabled) {
	259	frontswap_selfshrink();
	260	reset_timer = true;
	261	}
	262	#endif
	263	if (reset_timer)
	264	schedule_delayed_work(&selfballoon_worker,
	265	selfballoon_interval * HZ);
	266	}
	267
	268	#ifdef CONFIG_SYSFS
	269
a50777c7 DM	270	#include <linux/capability.h>
	271
	272	#define SELFBALLOON_SHOW(name, format, args...) \
07068021 KS	273	static ssize_t show_##name(struct device *dev, \
	274	struct device_attribute *attr, \
	275	char *buf) \
a50777c7 DM	276	{ \
	277	return sprintf(buf, format, ##args); \
	278	}
	279
	280	SELFBALLOON_SHOW(selfballooning, "%d\n", xen_selfballooning_enabled);
	281
07068021 KS	282	static ssize_t store_selfballooning(struct device *dev,
07068021 KS	283	struct device_attribute *attr,
a50777c7 DM	284	const char *buf,
	285	size_t count)
	286	{
	287	bool was_enabled = xen_selfballooning_enabled;
	288	unsigned long tmp;
	289	int err;
	290
	291	if (!capable(CAP_SYS_ADMIN))
	292	return -EPERM;
	293
	294	err = strict_strtoul(buf, 10, &tmp);
	295	if (err \|\| ((tmp != 0) && (tmp != 1)))
	296	return -EINVAL;
	297
	298	xen_selfballooning_enabled = !!tmp;
	299	if (!was_enabled && xen_selfballooning_enabled)
	300	schedule_delayed_work(&selfballoon_worker,
	301	selfballoon_interval * HZ);
	302
	303	return count;
	304	}
	305
07068021	306	static DEVICE_ATTR(selfballooning, S_IRUGO \| S_IWUSR,
a50777c7 DM	307	show_selfballooning, store_selfballooning);
	308
	309	SELFBALLOON_SHOW(selfballoon_interval, "%d\n", selfballoon_interval);
	310
07068021 KS	311	static ssize_t store_selfballoon_interval(struct device *dev,
07068021 KS	312	struct device_attribute *attr,
a50777c7 DM	313	const char *buf,
	314	size_t count)
	315	{
	316	unsigned long val;
	317	int err;
	318
	319	if (!capable(CAP_SYS_ADMIN))
	320	return -EPERM;
	321	err = strict_strtoul(buf, 10, &val);
	322	if (err \|\| val == 0)
	323	return -EINVAL;
	324	selfballoon_interval = val;
	325	return count;
	326	}
	327
07068021	328	static DEVICE_ATTR(selfballoon_interval, S_IRUGO \| S_IWUSR,
a50777c7 DM	329	show_selfballoon_interval, store_selfballoon_interval);
	330
	331	SELFBALLOON_SHOW(selfballoon_downhys, "%d\n", selfballoon_downhysteresis);
	332
07068021 KS	333	static ssize_t store_selfballoon_downhys(struct device *dev,
07068021 KS	334	struct device_attribute *attr,
a50777c7 DM	335	const char *buf,
	336	size_t count)
	337	{
	338	unsigned long val;
	339	int err;
	340
	341	if (!capable(CAP_SYS_ADMIN))
	342	return -EPERM;
	343	err = strict_strtoul(buf, 10, &val);
	344	if (err \|\| val == 0)
	345	return -EINVAL;
	346	selfballoon_downhysteresis = val;
	347	return count;
	348	}
	349
07068021	350	static DEVICE_ATTR(selfballoon_downhysteresis, S_IRUGO \| S_IWUSR,
a50777c7 DM	351	show_selfballoon_downhys, store_selfballoon_downhys);
	352
	353
	354	SELFBALLOON_SHOW(selfballoon_uphys, "%d\n", selfballoon_uphysteresis);
	355
07068021 KS	356	static ssize_t store_selfballoon_uphys(struct device *dev,
07068021 KS	357	struct device_attribute *attr,
a50777c7 DM	358	const char *buf,
	359	size_t count)
	360	{
	361	unsigned long val;
	362	int err;
	363
	364	if (!capable(CAP_SYS_ADMIN))
	365	return -EPERM;
	366	err = strict_strtoul(buf, 10, &val);
	367	if (err \|\| val == 0)
	368	return -EINVAL;
	369	selfballoon_uphysteresis = val;
	370	return count;
	371	}
	372
07068021	373	static DEVICE_ATTR(selfballoon_uphysteresis, S_IRUGO \| S_IWUSR,
a50777c7 DM	374	show_selfballoon_uphys, store_selfballoon_uphys);
a50777c7 DM	375
38a1ed4f DM	376	SELFBALLOON_SHOW(selfballoon_min_usable_mb, "%d\n",
	377	selfballoon_min_usable_mb);
	378
07068021 KS	379	static ssize_t store_selfballoon_min_usable_mb(struct device *dev,
07068021 KS	380	struct device_attribute *attr,
38a1ed4f DM	381	const char *buf,
	382	size_t count)
	383	{
	384	unsigned long val;
	385	int err;
	386
	387	if (!capable(CAP_SYS_ADMIN))
	388	return -EPERM;
	389	err = strict_strtoul(buf, 10, &val);
	390	if (err \|\| val == 0)
	391	return -EINVAL;
	392	selfballoon_min_usable_mb = val;
	393	return count;
	394	}
	395
07068021	396	static DEVICE_ATTR(selfballoon_min_usable_mb, S_IRUGO \| S_IWUSR,
38a1ed4f DM	397	show_selfballoon_min_usable_mb,
	398	store_selfballoon_min_usable_mb);
	399
	400
a50777c7 DM	401	#ifdef CONFIG_FRONTSWAP
	402	SELFBALLOON_SHOW(frontswap_selfshrinking, "%d\n", frontswap_selfshrinking);
	403
07068021 KS	404	static ssize_t store_frontswap_selfshrinking(struct device *dev,
07068021 KS	405	struct device_attribute *attr,
a50777c7 DM	406	const char *buf,
	407	size_t count)
	408	{
	409	bool was_enabled = frontswap_selfshrinking;
	410	unsigned long tmp;
	411	int err;
	412
	413	if (!capable(CAP_SYS_ADMIN))
	414	return -EPERM;
	415	err = strict_strtoul(buf, 10, &tmp);
	416	if (err \|\| ((tmp != 0) && (tmp != 1)))
	417	return -EINVAL;
	418	frontswap_selfshrinking = !!tmp;
	419	if (!was_enabled && !xen_selfballooning_enabled &&
	420	frontswap_selfshrinking)
	421	schedule_delayed_work(&selfballoon_worker,
	422	selfballoon_interval * HZ);
	423
	424	return count;
	425	}
	426
07068021	427	static DEVICE_ATTR(frontswap_selfshrinking, S_IRUGO \| S_IWUSR,
a50777c7 DM	428	show_frontswap_selfshrinking, store_frontswap_selfshrinking);
	429
	430	SELFBALLOON_SHOW(frontswap_inertia, "%d\n", frontswap_inertia);
	431
07068021 KS	432	static ssize_t store_frontswap_inertia(struct device *dev,
07068021 KS	433	struct device_attribute *attr,
a50777c7 DM	434	const char *buf,
	435	size_t count)
	436	{
	437	unsigned long val;
	438	int err;
	439
	440	if (!capable(CAP_SYS_ADMIN))
	441	return -EPERM;
	442	err = strict_strtoul(buf, 10, &val);
	443	if (err \|\| val == 0)
	444	return -EINVAL;
	445	frontswap_inertia = val;
	446	frontswap_inertia_counter = val;
	447	return count;
	448	}
	449
07068021	450	static DEVICE_ATTR(frontswap_inertia, S_IRUGO \| S_IWUSR,
a50777c7 DM	451	show_frontswap_inertia, store_frontswap_inertia);
	452
	453	SELFBALLOON_SHOW(frontswap_hysteresis, "%d\n", frontswap_hysteresis);
	454
07068021 KS	455	static ssize_t store_frontswap_hysteresis(struct device *dev,
07068021 KS	456	struct device_attribute *attr,
a50777c7 DM	457	const char *buf,
	458	size_t count)
	459	{
	460	unsigned long val;
	461	int err;
	462
	463	if (!capable(CAP_SYS_ADMIN))
	464	return -EPERM;
	465	err = strict_strtoul(buf, 10, &val);
	466	if (err \|\| val == 0)
	467	return -EINVAL;
	468	frontswap_hysteresis = val;
	469	return count;
	470	}
	471
07068021	472	static DEVICE_ATTR(frontswap_hysteresis, S_IRUGO \| S_IWUSR,
a50777c7 DM	473	show_frontswap_hysteresis, store_frontswap_hysteresis);
	474
	475	#endif /* CONFIG_FRONTSWAP */
	476
	477	static struct attribute *selfballoon_attrs[] = {
07068021 KS	478	&dev_attr_selfballooning.attr,
	479	&dev_attr_selfballoon_interval.attr,
	480	&dev_attr_selfballoon_downhysteresis.attr,
	481	&dev_attr_selfballoon_uphysteresis.attr,
	482	&dev_attr_selfballoon_min_usable_mb.attr,
a50777c7	483	#ifdef CONFIG_FRONTSWAP
07068021 KS	484	&dev_attr_frontswap_selfshrinking.attr,
	485	&dev_attr_frontswap_hysteresis.attr,
	486	&dev_attr_frontswap_inertia.attr,
a50777c7 DM	487	#endif
	488	NULL
	489	};
	490
	491	static struct attribute_group selfballoon_group = {
	492	.name = "selfballoon",
	493	.attrs = selfballoon_attrs
	494	};
	495	#endif
	496
07068021	497	int register_xen_selfballooning(struct device *dev)
a50777c7 DM	498	{
	499	int error = -1;
	500
	501	#ifdef CONFIG_SYSFS
07068021	502	error = sysfs_create_group(&dev->kobj, &selfballoon_group);
a50777c7 DM	503	#endif
	504	return error;
	505	}
	506	EXPORT_SYMBOL(register_xen_selfballooning);
	507
	508	static int __init xen_selfballoon_init(void)
	509	{
	510	bool enable = false;
	511
	512	if (!xen_domain())
	513	return -ENODEV;
	514
	515	if (xen_initial_domain()) {
	516	pr_info("xen/balloon: Xen selfballooning driver "
	517	"disabled for domain0.\n");
	518	return -ENODEV;
	519	}
	520
	521	xen_selfballooning_enabled = tmem_enabled && use_selfballooning;
	522	if (xen_selfballooning_enabled) {
	523	pr_info("xen/balloon: Initializing Xen "
	524	"selfballooning driver.\n");
	525	enable = true;
	526	}
	527	#ifdef CONFIG_FRONTSWAP
	528	frontswap_selfshrinking = tmem_enabled && use_frontswap_selfshrink;
	529	if (frontswap_selfshrinking) {
	530	pr_info("xen/balloon: Initializing frontswap "
	531	"selfshrinking driver.\n");
	532	enable = true;
	533	}
	534	#endif
	535	if (!enable)
	536	return -ENODEV;
	537
	538	schedule_delayed_work(&selfballoon_worker, selfballoon_interval * HZ);
	539
	540	return 0;
	541	}
	542
	543	subsys_initcall(xen_selfballoon_init);
	544
	545	MODULE_LICENSE("GPL");