[GitHub/mt8127/android_kernel_alcatel_ttab.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. 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.
 *
 */

#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;

/*
 * 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;
	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);
}

#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 = vm_memory_committed() +
				totalreserve_pages +
				MB2PAGES(selfballoon_reserved_mb);
#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);

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 = strict_strtoul(buf, 10, &val);
	if (err || 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 = 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,
	&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;

	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;
}
EXPORT_SYMBOL(xen_selfballoon_init);
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
37d46e15 KRW	56	* of the guest memory. Note, that selfballooning should be disabled by default
	57	* if frontswap is not configured. Similarly selfballooning should be enabled
	58	* by default if frontswap is configured and can be disabled with the
	59	* "tmem.selfballooning=0" kernel boot option. Finally, when frontswap is
	60	* configured, frontswap-selfshrinking can be disabled with the
	61	* "tmem.selfshrink=0" kernel boot option.
a50777c7 DM	62	*
	63	* Selfballooning is disallowed in domain0 and force-disabled.
	64	*
	65	*/
	66
	67	#include <linux/kernel.h>
38a1ed4f DM	68	#include <linux/bootmem.h>
38a1ed4f DM	69	#include <linux/swap.h>
a50777c7 DM	70	#include <linux/mm.h>
a50777c7 DM	71	#include <linux/mman.h>
4fec0e0b	72	#include <linux/module.h>
0642d2ed	73	#include <linux/workqueue.h>
cb0c05c5	74	#include <linux/device.h>
a50777c7	75	#include <xen/balloon.h>
a50777c7	76	#include <xen/tmem.h>
0642d2ed	77	#include <xen/xen.h>
a50777c7 DM	78
	79	/* Enable/disable with sysfs. */
	80	static int xen_selfballooning_enabled __read_mostly;
	81
	82	/*
	83	* Controls rate at which memory target (this iteration) approaches
	84	* ultimate goal when memory need is increasing (up-hysteresis) or
	85	* decreasing (down-hysteresis). Higher values of hysteresis cause
	86	* slower increases/decreases. The default values for the various
	87	* parameters were deemed reasonable by experimentation, may be
	88	* workload-dependent, and can all be adjusted via sysfs.
	89	*/
	90	static unsigned int selfballoon_downhysteresis __read_mostly = 8;
	91	static unsigned int selfballoon_uphysteresis __read_mostly = 1;
	92
	93	/* In HZ, controls frequency of worker invocation. */
	94	static unsigned int selfballoon_interval __read_mostly = 5;
	95
38a1ed4f DM	96	/*
	97	* Minimum usable RAM in MB for selfballooning target for balloon.
	98	* If non-zero, it is added to totalreserve_pages and self-ballooning
	99	* will not balloon below the sum. If zero, a piecewise linear function
	100	* is calculated as a minimum and added to totalreserve_pages. Note that
	101	* setting this value indiscriminately may cause OOMs and crashes.
	102	*/
	103	static unsigned int selfballoon_min_usable_mb;
	104
d79d5959 JS	105	/*
	106	* Amount of RAM in MB to add to the target number of pages.
	107	* Can be used to reserve some more room for caches and the like.
	108	*/
	109	static unsigned int selfballoon_reserved_mb;
	110
a50777c7 DM	111	static void selfballoon_process(struct work_struct *work);
	112	static DECLARE_DELAYED_WORK(selfballoon_worker, selfballoon_process);
	113
	114	#ifdef CONFIG_FRONTSWAP
	115	#include <linux/frontswap.h>
	116
	117	/* Enable/disable with sysfs. */
	118	static bool frontswap_selfshrinking __read_mostly;
	119
a50777c7 DM	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
a50777c7 DM	173	#endif /* CONFIG_FRONTSWAP */
a50777c7 DM	174
38a1ed4f DM	175	#define MB2PAGES(mb) ((mb) << (20 - PAGE_SHIFT))
38a1ed4f DM	176
a50777c7 DM	177	/*
	178	* Use current balloon size, the goal (vm_committed_as), and hysteresis
	179	* parameters to set a new target balloon size
	180	*/
	181	static void selfballoon_process(struct work_struct *work)
	182	{
38a1ed4f DM	183	unsigned long cur_pages, goal_pages, tgt_pages, floor_pages;
38a1ed4f DM	184	unsigned long useful_pages;
a50777c7 DM	185	bool reset_timer = false;
	186
	187	if (xen_selfballooning_enabled) {
38a1ed4f	188	cur_pages = totalram_pages;
a50777c7	189	tgt_pages = cur_pages; /* default is no change */
997071bc	190	goal_pages = vm_memory_committed() +
d79d5959 JS	191	totalreserve_pages +
d79d5959 JS	192	MB2PAGES(selfballoon_reserved_mb);
a50777c7 DM	193	#ifdef CONFIG_FRONTSWAP
	194	/* allow space for frontswap pages to be repatriated */
	195	if (frontswap_selfshrinking && frontswap_enabled)
	196	goal_pages += frontswap_curr_pages();
	197	#endif
	198	if (cur_pages > goal_pages)
	199	tgt_pages = cur_pages -
	200	((cur_pages - goal_pages) /
	201	selfballoon_downhysteresis);
	202	else if (cur_pages < goal_pages)
	203	tgt_pages = cur_pages +
	204	((goal_pages - cur_pages) /
	205	selfballoon_uphysteresis);
	206	/* else if cur_pages == goal_pages, no change */
38a1ed4f DM	207	useful_pages = max_pfn - totalreserve_pages;
	208	if (selfballoon_min_usable_mb != 0)
	209	floor_pages = totalreserve_pages +
	210	MB2PAGES(selfballoon_min_usable_mb);
	211	/* piecewise linear function ending in ~3% slope */
	212	else if (useful_pages < MB2PAGES(16))
	213	floor_pages = max_pfn; /* not worth ballooning */
	214	else if (useful_pages < MB2PAGES(64))
	215	floor_pages = totalreserve_pages + MB2PAGES(16) +
	216	((useful_pages - MB2PAGES(16)) >> 1);
	217	else if (useful_pages < MB2PAGES(512))
	218	floor_pages = totalreserve_pages + MB2PAGES(40) +
	219	((useful_pages - MB2PAGES(40)) >> 3);
	220	else /* useful_pages >= MB2PAGES(512) */
	221	floor_pages = totalreserve_pages + MB2PAGES(99) +
	222	((useful_pages - MB2PAGES(99)) >> 5);
	223	if (tgt_pages < floor_pages)
	224	tgt_pages = floor_pages;
	225	balloon_set_new_target(tgt_pages +
	226	balloon_stats.current_pages - totalram_pages);
a50777c7 DM	227	reset_timer = true;
	228	}
	229	#ifdef CONFIG_FRONTSWAP
	230	if (frontswap_selfshrinking && frontswap_enabled) {
	231	frontswap_selfshrink();
	232	reset_timer = true;
	233	}
	234	#endif
	235	if (reset_timer)
	236	schedule_delayed_work(&selfballoon_worker,
	237	selfballoon_interval * HZ);
	238	}
	239
	240	#ifdef CONFIG_SYSFS
	241
a50777c7 DM	242	#include <linux/capability.h>
	243
	244	#define SELFBALLOON_SHOW(name, format, args...) \
07068021 KS	245	static ssize_t show_##name(struct device *dev, \
	246	struct device_attribute *attr, \
	247	char *buf) \
a50777c7 DM	248	{ \
	249	return sprintf(buf, format, ##args); \
	250	}
	251
	252	SELFBALLOON_SHOW(selfballooning, "%d\n", xen_selfballooning_enabled);
	253
07068021 KS	254	static ssize_t store_selfballooning(struct device *dev,
07068021 KS	255	struct device_attribute *attr,
a50777c7 DM	256	const char *buf,
	257	size_t count)
	258	{
	259	bool was_enabled = xen_selfballooning_enabled;
	260	unsigned long tmp;
	261	int err;
	262
	263	if (!capable(CAP_SYS_ADMIN))
	264	return -EPERM;
	265
	266	err = strict_strtoul(buf, 10, &tmp);
	267	if (err \|\| ((tmp != 0) && (tmp != 1)))
	268	return -EINVAL;
	269
	270	xen_selfballooning_enabled = !!tmp;
	271	if (!was_enabled && xen_selfballooning_enabled)
	272	schedule_delayed_work(&selfballoon_worker,
	273	selfballoon_interval * HZ);
	274
	275	return count;
	276	}
	277
07068021	278	static DEVICE_ATTR(selfballooning, S_IRUGO \| S_IWUSR,
a50777c7 DM	279	show_selfballooning, store_selfballooning);
	280
	281	SELFBALLOON_SHOW(selfballoon_interval, "%d\n", selfballoon_interval);
	282
07068021 KS	283	static ssize_t store_selfballoon_interval(struct device *dev,
07068021 KS	284	struct device_attribute *attr,
a50777c7 DM	285	const char *buf,
	286	size_t count)
	287	{
	288	unsigned long val;
	289	int err;
	290
	291	if (!capable(CAP_SYS_ADMIN))
	292	return -EPERM;
	293	err = strict_strtoul(buf, 10, &val);
	294	if (err \|\| val == 0)
	295	return -EINVAL;
	296	selfballoon_interval = val;
	297	return count;
	298	}
	299
07068021	300	static DEVICE_ATTR(selfballoon_interval, S_IRUGO \| S_IWUSR,
a50777c7 DM	301	show_selfballoon_interval, store_selfballoon_interval);
	302
	303	SELFBALLOON_SHOW(selfballoon_downhys, "%d\n", selfballoon_downhysteresis);
	304
07068021 KS	305	static ssize_t store_selfballoon_downhys(struct device *dev,
07068021 KS	306	struct device_attribute *attr,
a50777c7 DM	307	const char *buf,
	308	size_t count)
	309	{
	310	unsigned long val;
	311	int err;
	312
	313	if (!capable(CAP_SYS_ADMIN))
	314	return -EPERM;
	315	err = strict_strtoul(buf, 10, &val);
	316	if (err \|\| val == 0)
	317	return -EINVAL;
	318	selfballoon_downhysteresis = val;
	319	return count;
	320	}
	321
07068021	322	static DEVICE_ATTR(selfballoon_downhysteresis, S_IRUGO \| S_IWUSR,
a50777c7 DM	323	show_selfballoon_downhys, store_selfballoon_downhys);
	324
	325
	326	SELFBALLOON_SHOW(selfballoon_uphys, "%d\n", selfballoon_uphysteresis);
	327
07068021 KS	328	static ssize_t store_selfballoon_uphys(struct device *dev,
07068021 KS	329	struct device_attribute *attr,
a50777c7 DM	330	const char *buf,
	331	size_t count)
	332	{
	333	unsigned long val;
	334	int err;
	335
	336	if (!capable(CAP_SYS_ADMIN))
	337	return -EPERM;
	338	err = strict_strtoul(buf, 10, &val);
	339	if (err \|\| val == 0)
	340	return -EINVAL;
	341	selfballoon_uphysteresis = val;
	342	return count;
	343	}
	344
07068021	345	static DEVICE_ATTR(selfballoon_uphysteresis, S_IRUGO \| S_IWUSR,
a50777c7 DM	346	show_selfballoon_uphys, store_selfballoon_uphys);
a50777c7 DM	347
38a1ed4f DM	348	SELFBALLOON_SHOW(selfballoon_min_usable_mb, "%d\n",
	349	selfballoon_min_usable_mb);
	350
07068021 KS	351	static ssize_t store_selfballoon_min_usable_mb(struct device *dev,
07068021 KS	352	struct device_attribute *attr,
38a1ed4f DM	353	const char *buf,
	354	size_t count)
	355	{
	356	unsigned long val;
	357	int err;
	358
	359	if (!capable(CAP_SYS_ADMIN))
	360	return -EPERM;
	361	err = strict_strtoul(buf, 10, &val);
	362	if (err \|\| val == 0)
	363	return -EINVAL;
	364	selfballoon_min_usable_mb = val;
	365	return count;
	366	}
	367
07068021	368	static DEVICE_ATTR(selfballoon_min_usable_mb, S_IRUGO \| S_IWUSR,
38a1ed4f DM	369	show_selfballoon_min_usable_mb,
	370	store_selfballoon_min_usable_mb);
	371
d79d5959 JS	372	SELFBALLOON_SHOW(selfballoon_reserved_mb, "%d\n",
	373	selfballoon_reserved_mb);
	374
	375	static ssize_t store_selfballoon_reserved_mb(struct device *dev,
	376	struct device_attribute *attr,
	377	const char *buf,
	378	size_t count)
	379	{
	380	unsigned long val;
	381	int err;
	382
	383	if (!capable(CAP_SYS_ADMIN))
	384	return -EPERM;
	385	err = strict_strtoul(buf, 10, &val);
	386	if (err \|\| val == 0)
	387	return -EINVAL;
	388	selfballoon_reserved_mb = val;
	389	return count;
	390	}
	391
	392	static DEVICE_ATTR(selfballoon_reserved_mb, S_IRUGO \| S_IWUSR,
	393	show_selfballoon_reserved_mb,
	394	store_selfballoon_reserved_mb);
	395
38a1ed4f	396
a50777c7 DM	397	#ifdef CONFIG_FRONTSWAP
	398	SELFBALLOON_SHOW(frontswap_selfshrinking, "%d\n", frontswap_selfshrinking);
	399
07068021 KS	400	static ssize_t store_frontswap_selfshrinking(struct device *dev,
07068021 KS	401	struct device_attribute *attr,
a50777c7 DM	402	const char *buf,
	403	size_t count)
	404	{
	405	bool was_enabled = frontswap_selfshrinking;
	406	unsigned long tmp;
	407	int err;
	408
	409	if (!capable(CAP_SYS_ADMIN))
	410	return -EPERM;
	411	err = strict_strtoul(buf, 10, &tmp);
	412	if (err \|\| ((tmp != 0) && (tmp != 1)))
	413	return -EINVAL;
	414	frontswap_selfshrinking = !!tmp;
	415	if (!was_enabled && !xen_selfballooning_enabled &&
	416	frontswap_selfshrinking)
	417	schedule_delayed_work(&selfballoon_worker,
	418	selfballoon_interval * HZ);
	419
	420	return count;
	421	}
	422
07068021	423	static DEVICE_ATTR(frontswap_selfshrinking, S_IRUGO \| S_IWUSR,
a50777c7 DM	424	show_frontswap_selfshrinking, store_frontswap_selfshrinking);
	425
	426	SELFBALLOON_SHOW(frontswap_inertia, "%d\n", frontswap_inertia);
	427
07068021 KS	428	static ssize_t store_frontswap_inertia(struct device *dev,
07068021 KS	429	struct device_attribute *attr,
a50777c7 DM	430	const char *buf,
	431	size_t count)
	432	{
	433	unsigned long val;
	434	int err;
	435
	436	if (!capable(CAP_SYS_ADMIN))
	437	return -EPERM;
	438	err = strict_strtoul(buf, 10, &val);
	439	if (err \|\| val == 0)
	440	return -EINVAL;
	441	frontswap_inertia = val;
	442	frontswap_inertia_counter = val;
	443	return count;
	444	}
	445
07068021	446	static DEVICE_ATTR(frontswap_inertia, S_IRUGO \| S_IWUSR,
a50777c7 DM	447	show_frontswap_inertia, store_frontswap_inertia);
	448
	449	SELFBALLOON_SHOW(frontswap_hysteresis, "%d\n", frontswap_hysteresis);
	450
07068021 KS	451	static ssize_t store_frontswap_hysteresis(struct device *dev,
07068021 KS	452	struct device_attribute *attr,
a50777c7 DM	453	const char *buf,
	454	size_t count)
	455	{
	456	unsigned long val;
	457	int err;
	458
	459	if (!capable(CAP_SYS_ADMIN))
	460	return -EPERM;
	461	err = strict_strtoul(buf, 10, &val);
	462	if (err \|\| val == 0)
	463	return -EINVAL;
	464	frontswap_hysteresis = val;
	465	return count;
	466	}
	467
07068021	468	static DEVICE_ATTR(frontswap_hysteresis, S_IRUGO \| S_IWUSR,
a50777c7 DM	469	show_frontswap_hysteresis, store_frontswap_hysteresis);
	470
	471	#endif /* CONFIG_FRONTSWAP */
	472
	473	static struct attribute *selfballoon_attrs[] = {
07068021 KS	474	&dev_attr_selfballooning.attr,
	475	&dev_attr_selfballoon_interval.attr,
	476	&dev_attr_selfballoon_downhysteresis.attr,
	477	&dev_attr_selfballoon_uphysteresis.attr,
	478	&dev_attr_selfballoon_min_usable_mb.attr,
d79d5959	479	&dev_attr_selfballoon_reserved_mb.attr,
a50777c7	480	#ifdef CONFIG_FRONTSWAP
07068021 KS	481	&dev_attr_frontswap_selfshrinking.attr,
	482	&dev_attr_frontswap_hysteresis.attr,
	483	&dev_attr_frontswap_inertia.attr,
a50777c7 DM	484	#endif
	485	NULL
	486	};
	487
ead1d014	488	static const struct attribute_group selfballoon_group = {
a50777c7 DM	489	.name = "selfballoon",
	490	.attrs = selfballoon_attrs
	491	};
	492	#endif
	493
07068021	494	int register_xen_selfballooning(struct device *dev)
a50777c7 DM	495	{
	496	int error = -1;
	497
	498	#ifdef CONFIG_SYSFS
07068021	499	error = sysfs_create_group(&dev->kobj, &selfballoon_group);
a50777c7 DM	500	#endif
	501	return error;
	502	}
	503	EXPORT_SYMBOL(register_xen_selfballooning);
	504
10a7a077	505	int xen_selfballoon_init(bool use_selfballooning, bool use_frontswap_selfshrink)
a50777c7 DM	506	{
	507	bool enable = false;
	508
	509	if (!xen_domain())
	510	return -ENODEV;
	511
	512	if (xen_initial_domain()) {
	513	pr_info("xen/balloon: Xen selfballooning driver "
	514	"disabled for domain0.\n");
	515	return -ENODEV;
	516	}
	517
	518	xen_selfballooning_enabled = tmem_enabled && use_selfballooning;
	519	if (xen_selfballooning_enabled) {
	520	pr_info("xen/balloon: Initializing Xen "
	521	"selfballooning driver.\n");
	522	enable = true;
	523	}
	524	#ifdef CONFIG_FRONTSWAP
	525	frontswap_selfshrinking = tmem_enabled && use_frontswap_selfshrink;
	526	if (frontswap_selfshrinking) {
	527	pr_info("xen/balloon: Initializing frontswap "
	528	"selfshrinking driver.\n");
	529	enable = true;
	530	}
	531	#endif
	532	if (!enable)
	533	return -ENODEV;
	534
	535	schedule_delayed_work(&selfballoon_worker, selfballoon_interval * HZ);
	536
	537	return 0;
	538	}
10a7a077	539	EXPORT_SYMBOL(xen_selfballoon_init);