Release 4.8 mm/vmstat.c

/*
 *  linux/mm/vmstat.c
 *
 *  Manages VM statistics
 *  Copyright (C) 1991, 1992, 1993, 1994  Linus Torvalds
 *
 *  zoned VM statistics
 *  Copyright (C) 2006 Silicon Graphics, Inc.,
 *              Christoph Lameter <christoph@lameter.com>
 *  Copyright (C) 2008-2014 Christoph Lameter
 */
#include <linux/fs.h>
#include <linux/mm.h>
#include <linux/err.h>
#include <linux/module.h>
#include <linux/slab.h>
#include <linux/cpu.h>
#include <linux/cpumask.h>
#include <linux/vmstat.h>
#include <linux/proc_fs.h>
#include <linux/seq_file.h>
#include <linux/debugfs.h>
#include <linux/sched.h>
#include <linux/math64.h>
#include <linux/writeback.h>
#include <linux/compaction.h>
#include <linux/mm_inline.h>
#include <linux/page_ext.h>
#include <linux/page_owner.h>

#include "internal.h"

#ifdef CONFIG_VM_EVENT_COUNTERS
DEFINE_PER_CPU(struct vm_event_state, vm_event_states) = {{0}};

EXPORT_PER_CPU_SYMBOL(vm_event_states);



static void sum_vm_events(unsigned long *ret)
{
	int cpu;
	int i;

	memset(ret, 0, NR_VM_EVENT_ITEMS * sizeof(unsigned long));

	for_each_online_cpu(cpu) {
		struct vm_event_state *this = &per_cpu(vm_event_states, cpu);

		for (i = 0; i < NR_VM_EVENT_ITEMS; i++)
			ret[i] += this->event[i];
	}
}

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/*
 * Accumulate the vm event counters across all CPUs.
 * The result is unavoidably approximate - it can change
 * during and after execution of this function.
*/


void all_vm_events(unsigned long *ret)
{
	get_online_cpus();
	sum_vm_events(ret);
	put_online_cpus();
}
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EXPORT_SYMBOL_GPL(all_vm_events);

/*
 * Fold the foreign cpu events into our own.
 *
 * This is adding to the events on one processor
 * but keeps the global counts constant.
 */


void vm_events_fold_cpu(int cpu)
{
	struct vm_event_state *fold_state = &per_cpu(vm_event_states, cpu);
	int i;

	for (i = 0; i < NR_VM_EVENT_ITEMS; i++) {
		count_vm_events(i, fold_state->event[i]);
		fold_state->event[i] = 0;
	}
}

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#endif /* CONFIG_VM_EVENT_COUNTERS */

/*
 * Manage combined zone based / global counters
 *
 * vm_stat contains the global counters
 */

atomic_long_t vm_zone_stat[NR_VM_ZONE_STAT_ITEMS] __cacheline_aligned_in_smp;

atomic_long_t vm_node_stat[NR_VM_NODE_STAT_ITEMS] __cacheline_aligned_in_smp;

EXPORT_SYMBOL(vm_zone_stat);

EXPORT_SYMBOL(vm_node_stat);

#ifdef CONFIG_SMP



int calculate_pressure_threshold(struct zone *zone)
{
	int threshold;
	int watermark_distance;

	/*
         * As vmstats are not up to date, there is drift between the estimated
         * and real values. For high thresholds and a high number of CPUs, it
         * is possible for the min watermark to be breached while the estimated
         * value looks fine. The pressure threshold is a reduced value such
         * that even the maximum amount of drift will not accidentally breach
         * the min watermark
         */
	watermark_distance = low_wmark_pages(zone) - min_wmark_pages(zone);
	threshold = max(1, (int)(watermark_distance / num_online_cpus()));

	/*
         * Maximum threshold is 125
         */
	threshold = min(125, threshold);

	return threshold;
}

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int calculate_normal_threshold(struct zone *zone)
{
	int threshold;
	int mem;	/* memory in 128 MB units */

	/*
         * The threshold scales with the number of processors and the amount
         * of memory per zone. More memory means that we can defer updates for
         * longer, more processors could lead to more contention.
         * fls() is used to have a cheap way of logarithmic scaling.
         *
         * Some sample thresholds:
         *
         * Threshold    Processors      (fls)   Zonesize        fls(mem+1)
         * ------------------------------------------------------------------
         * 8            1               1       0.9-1 GB        4
         * 16           2               2       0.9-1 GB        4
         * 20           2               2       1-2 GB          5
         * 24           2               2       2-4 GB          6
         * 28           2               2       4-8 GB          7
         * 32           2               2       8-16 GB         8
         * 4            2               2       <128M           1
         * 30           4               3       2-4 GB          5
         * 48           4               3       8-16 GB         8
         * 32           8               4       1-2 GB          4
         * 32           8               4       0.9-1GB         4
         * 10           16              5       <128M           1
         * 40           16              5       900M            4
         * 70           64              7       2-4 GB          5
         * 84           64              7       4-8 GB          6
         * 108          512             9       4-8 GB          6
         * 125          1024            10      8-16 GB         8
         * 125          1024            10      16-32 GB        9
         */

	mem = zone->managed_pages >> (27 - PAGE_SHIFT);

	threshold = 2 * fls(num_online_cpus()) * (1 + fls(mem));

	/*
         * Maximum threshold is 125
         */
	threshold = min(125, threshold);

	return threshold;
}

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/*
 * Refresh the thresholds for each zone.
 */


void refresh_zone_stat_thresholds(void)
{
	struct pglist_data *pgdat;
	struct zone *zone;
	int cpu;
	int threshold;

	/* Zero current pgdat thresholds */
	for_each_online_pgdat(pgdat) {
		for_each_online_cpu(cpu) {
			per_cpu_ptr(pgdat->per_cpu_nodestats, cpu)->stat_threshold = 0;
		}
	}

	for_each_populated_zone(zone) {
		struct pglist_data *pgdat = zone->zone_pgdat;
		unsigned long max_drift, tolerate_drift;

		threshold = calculate_normal_threshold(zone);

		for_each_online_cpu(cpu) {
			int pgdat_threshold;

			per_cpu_ptr(zone->pageset, cpu)->stat_threshold
							= threshold;

			/* Base nodestat threshold on the largest populated zone. */
			pgdat_threshold = per_cpu_ptr(pgdat->per_cpu_nodestats, cpu)->stat_threshold;
			per_cpu_ptr(pgdat->per_cpu_nodestats, cpu)->stat_threshold
				= max(threshold, pgdat_threshold);
		}

		/*
                 * Only set percpu_drift_mark if there is a danger that
                 * NR_FREE_PAGES reports the low watermark is ok when in fact
                 * the min watermark could be breached by an allocation
                 */
		tolerate_drift = low_wmark_pages(zone) - min_wmark_pages(zone);
		max_drift = num_online_cpus() * threshold;
		if (max_drift > tolerate_drift)
			zone->percpu_drift_mark = high_wmark_pages(zone) +
					max_drift;
	}
}

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void set_pgdat_percpu_threshold(pg_data_t *pgdat,
				int (*calculate_pressure)(struct zone *))
{
	struct zone *zone;
	int cpu;
	int threshold;
	int i;

	for (i = 0; i < pgdat->nr_zones; i++) {
		zone = &pgdat->node_zones[i];
		if (!zone->percpu_drift_mark)
			continue;

		threshold = (*calculate_pressure)(zone);
		for_each_online_cpu(cpu)
			per_cpu_ptr(zone->pageset, cpu)->stat_threshold
							= threshold;
	}
}

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/*
 * For use when we know that interrupts are disabled,
 * or when we know that preemption is disabled and that
 * particular counter cannot be updated from interrupt context.
 */


void __mod_zone_page_state(struct zone *zone, enum zone_stat_item item,
			   long delta)
{
	struct per_cpu_pageset __percpu *pcp = zone->pageset;
	s8 __percpu *p = pcp->vm_stat_diff + item;
	long x;
	long t;

	x = delta + __this_cpu_read(*p);

	t = __this_cpu_read(pcp->stat_threshold);

	if (unlikely(x > t || x < -t)) {
		zone_page_state_add(x, zone, item);
		x = 0;
	}
	__this_cpu_write(*p, x);
}
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EXPORT_SYMBOL(__mod_zone_page_state);



void __mod_node_page_state(struct pglist_data *pgdat, enum node_stat_item item,
				long delta)
{
	struct per_cpu_nodestat __percpu *pcp = pgdat->per_cpu_nodestats;
	s8 __percpu *p = pcp->vm_node_stat_diff + item;
	long x;
	long t;

	x = delta + __this_cpu_read(*p);

	t = __this_cpu_read(pcp->stat_threshold);

	if (unlikely(x > t || x < -t)) {
		node_page_state_add(x, pgdat, item);
		x = 0;
	}
	__this_cpu_write(*p, x);
}
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EXPORT_SYMBOL(__mod_node_page_state);

/*
 * Optimized increment and decrement functions.
 *
 * These are only for a single page and therefore can take a struct page *
 * argument instead of struct zone *. This allows the inclusion of the code
 * generated for page_zone(page) into the optimized functions.
 *
 * No overflow check is necessary and therefore the differential can be
 * incremented or decremented in place which may allow the compilers to
 * generate better code.
 * The increment or decrement is known and therefore one boundary check can
 * be omitted.
 *
 * NOTE: These functions are very performance sensitive. Change only
 * with care.
 *
 * Some processors have inc/dec instructions that are atomic vs an interrupt.
 * However, the code must first determine the differential location in a zone
 * based on the processor number and then inc/dec the counter. There is no
 * guarantee without disabling preemption that the processor will not change
 * in between and therefore the atomicity vs. interrupt cannot be exploited
 * in a useful way here.
 */


void __inc_zone_state(struct zone *zone, enum zone_stat_item item)
{
	struct per_cpu_pageset __percpu *pcp = zone->pageset;
	s8 __percpu *p = pcp->vm_stat_diff + item;
	s8 v, t;

	v = __this_cpu_inc_return(*p);
	t = __this_cpu_read(pcp->stat_threshold);
	if (unlikely(v > t)) {
		s8 overstep = t >> 1;

		zone_page_state_add(v + overstep, zone, item);
		__this_cpu_write(*p, -overstep);
	}
}

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void __inc_node_state(struct pglist_data *pgdat, enum node_stat_item item)
{
	struct per_cpu_nodestat __percpu *pcp = pgdat->per_cpu_nodestats;
	s8 __percpu *p = pcp->vm_node_stat_diff + item;
	s8 v, t;

	v = __this_cpu_inc_return(*p);
	t = __this_cpu_read(pcp->stat_threshold);
	if (unlikely(v > t)) {
		s8 overstep = t >> 1;

		node_page_state_add(v + overstep, pgdat, item);
		__this_cpu_write(*p, -overstep);
	}
}

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void __inc_zone_page_state(struct page *page, enum zone_stat_item item)
{
	__inc_zone_state(page_zone(page), item);
}
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EXPORT_SYMBOL(__inc_zone_page_state);



void __inc_node_page_state(struct page *page, enum node_stat_item item)
{
	__inc_node_state(page_pgdat(page), item);
}
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EXPORT_SYMBOL(__inc_node_page_state);



void __dec_zone_state(struct zone *zone, enum zone_stat_item item)
{
	struct per_cpu_pageset __percpu *pcp = zone->pageset;
	s8 __percpu *p = pcp->vm_stat_diff + item;
	s8 v, t;

	v = __this_cpu_dec_return(*p);
	t = __this_cpu_read(pcp->stat_threshold);
	if (unlikely(v < - t)) {
		s8 overstep = t >> 1;

		zone_page_state_add(v - overstep, zone, item);
		__this_cpu_write(*p, overstep);
	}
}

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void __dec_node_state(struct pglist_data *pgdat, enum node_stat_item item)
{
	struct per_cpu_nodestat __percpu *pcp = pgdat->per_cpu_nodestats;
	s8 __percpu *p = pcp->vm_node_stat_diff + item;
	s8 v, t;

	v = __this_cpu_dec_return(*p);
	t = __this_cpu_read(pcp->stat_threshold);
	if (unlikely(v < - t)) {
		s8 overstep = t >> 1;

		node_page_state_add(v - overstep, pgdat, item);
		__this_cpu_write(*p, overstep);
	}
}

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void __dec_zone_page_state(struct page *page, enum zone_stat_item item)
{
	__dec_zone_state(page_zone(page), item);
}
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EXPORT_SYMBOL(__dec_zone_page_state);



void __dec_node_page_state(struct page *page, enum node_stat_item item)
{
	__dec_node_state(page_pgdat(page), item);
}
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EXPORT_SYMBOL(__dec_node_page_state);

#ifdef CONFIG_HAVE_CMPXCHG_LOCAL
/*
 * If we have cmpxchg_local support then we do not need to incur the overhead
 * that comes with local_irq_save/restore if we use this_cpu_cmpxchg.
 *
 * mod_state() modifies the zone counter state through atomic per cpu
 * operations.
 *
 * Overstep mode specifies how overstep should handled:
 *     0       No overstepping
 *     1       Overstepping half of threshold
 *     -1      Overstepping minus half of threshold
*/


static inline void mod_zone_state(struct zone *zone,
       enum zone_stat_item item, long delta, int overstep_mode)
{
	struct per_cpu_pageset __percpu *pcp = zone->pageset;
	s8 __percpu *p = pcp->vm_stat_diff + item;
	long o, n, t, z;

	do {
		z = 0;  /* overflow to zone counters */

		/*
                 * The fetching of the stat_threshold is racy. We may apply
                 * a counter threshold to the wrong the cpu if we get
                 * rescheduled while executing here. However, the next
                 * counter update will apply the threshold again and
                 * therefore bring the counter under the threshold again.
                 *
                 * Most of the time the thresholds are the same anyways
                 * for all cpus in a zone.
                 */
		t = this_cpu_read(pcp->stat_threshold);

		o = this_cpu_read(*p);
		n = delta + o;

		if (n > t || n < -t) {
			int os = overstep_mode * (t >> 1) ;

			/* Overflow must be added to zone counters */
			z = n + os;
			n = -os;
		}
	} while (this_cpu_cmpxchg(*p, o, n) != o);

	if (z)
		zone_page_state_add(z, zone, item);
}

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void mod_zone_page_state(struct zone *zone, enum zone_stat_item item,
			 long delta)
{
	mod_zone_state(zone, item, delta, 0);
}
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EXPORT_SYMBOL(mod_zone_page_state);



void inc_zone_page_state(struct page *page, enum zone_stat_item item)
{
	mod_zone_state(page_zone(page), item, 1, 1);
}
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EXPORT_SYMBOL(inc_zone_page_state);



void dec_zone_page_state(struct page *page, enum zone_stat_item item)
{
	mod_zone_state(page_zone(page), item, -1, -1);
}
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EXPORT_SYMBOL(dec_zone_page_state);



static inline void mod_node_state(struct pglist_data *pgdat,
       enum node_stat_item item, int delta, int overstep_mode)
{
	struct per_cpu_nodestat __percpu *pcp = pgdat->per_cpu_nodestats;
	s8 __percpu *p = pcp->vm_node_stat_diff + item;
	long o, n, t, z;

	do {
		z = 0;  /* overflow to node counters */

		/*
                 * The fetching of the stat_threshold is racy. We may apply
                 * a counter threshold to the wrong the cpu if we get
                 * rescheduled while executing here. However, the next
                 * counter update will apply the threshold again and
                 * therefore bring the counter under the threshold again.
                 *
                 * Most of the time the thresholds are the same anyways
                 * for all cpus in a node.
                 */
		t = this_cpu_read(pcp->stat_threshold);

		o = this_cpu_read(*p);
		n = delta + o;

		if (n > t || n < -t) {
			int os = overstep_mode * (t >> 1) ;

			/* Overflow must be added to node counters */
			z = n + os;
			n = -os;
		}
	} while (this_cpu_cmpxchg(*p, o, n) != o);

	if (z)
		node_page_state_add(z, pgdat, item);
}

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void mod_node_page_state(struct pglist_data *pgdat, enum node_stat_item item,
					long delta)
{
	mod_node_state(pgdat, item, delta, 0);
}
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EXPORT_SYMBOL(mod_node_page_state);



void inc_node_state(struct pglist_data *pgdat, enum node_stat_item item)
{
	mod_node_state(pgdat, item, 1, 1);
}

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void inc_node_page_state(struct page *page, enum node_stat_item item)
{
	mod_node_state(page_pgdat(page), item, 1, 1);
}
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EXPORT_SYMBOL(inc_node_page_state);



void dec_node_page_state(struct page *page, enum node_stat_item item)
{
	mod_node_state(page_pgdat(page), item, -1, -1);
}
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EXPORT_SYMBOL(dec_node_page_state);
#else
/*
 * Use interrupt disable to serialize counter updates
 */


void mod_zone_page_state(struct zone *zone, enum zone_stat_item item,
			 long delta)
{
	unsigned long flags;

	local_irq_save(flags);
	__mod_zone_page_state(zone, item, delta);
	local_irq_restore(flags);
}
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EXPORT_SYMBOL(mod_zone_page_state);



void inc_zone_page_state(struct page *page, enum zone_stat_item item)
{
	unsigned long flags;
	struct zone *zone;

	zone = page_zone(page);
	local_irq_save(flags);
	__inc_zone_state(zone, item);
	local_irq_restore(flags);
}
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EXPORT_SYMBOL(inc_zone_page_state);



void dec_zone_page_state(struct page *page, enum zone_stat_item item)
{
	unsigned long flags;

	local_irq_save(flags);
	__dec_zone_page_state(page, item);
	local_irq_restore(flags);
}
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EXPORT_SYMBOL(dec_zone_page_state);



void inc_node_state(struct pglist_data *pgdat, enum node_stat_item item)
{
	unsigned long flags;

	local_irq_save(flags);
	__inc_node_state(pgdat, item);
	local_irq_restore(flags);
}
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EXPORT_SYMBOL(inc_node_state);



void mod_node_page_state(struct pglist_data *pgdat, enum node_stat_item item,
					long delta)
{
	unsigned long flags;

	local_irq_save(flags);
	__mod_node_page_state(pgdat, item, delta);
	local_irq_restore(flags);
}
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EXPORT_SYMBOL(mod_node_page_state);



void inc_node_page_state(struct page *page, enum node_stat_item item)
{
	unsigned long flags;
	struct pglist_data *pgdat;

	pgdat = page_pgdat(page);
	local_irq_save(flags);
	__inc_node_state(pgdat, item);
	local_irq_restore(flags);
}
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EXPORT_SYMBOL(inc_node_page_state);



void dec_node_page_state(struct page *page, enum node_stat_item item)
{
	unsigned long flags;

	local_irq_save(flags);
	__dec_node_page_state(page, item);
	local_irq_restore(flags);
}
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EXPORT_SYMBOL(dec_node_page_state);
#endif

/*
 * Fold a differential into the global counters.
 * Returns the number of counters updated.
 */


static int fold_diff(int *zone_diff, int *node_diff)
{
	int i;
	int changes = 0;

	for (i = 0; i < NR_VM_ZONE_STAT_ITEMS; i++)
		if (zone_diff[i]) {
			atomic_long_add(zone_diff[i], &vm_zone_stat[i]);
			changes++;
	}

	for (i = 0; i < NR_VM_NODE_STAT_ITEMS; i++)
		if (node_diff[i]) {
			atomic_long_add(node_diff[i], &vm_node_stat[i]);
			changes++;
	}
	return changes;
}

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/*
 * Update the zone counters for the current cpu.
 *
 * Note that refresh_cpu_vm_stats strives to only access
 * node local memory. The per cpu pagesets on remote zones are placed
 * in the memory local to the processor using that pageset. So the
 * loop over all zones will access a series of cachelines local to
 * the processor.
 *
 * The call to zone_page_state_add updates the cachelines with the
 * statistics in the remote zone struct as well as the global cachelines
 * with the global counters. These could cause remote node cache line
 * bouncing and will have to be only done when necessary.
 *
 * The function returns the number of global counters updated.
 */


static int refresh_cpu_vm_stats(bool do_pagesets)
{
	struct pglist_data *pgdat;
	struct zone *zone;
	int i;
	int global_zone_diff[NR_VM_ZONE_STAT_ITEMS] = { 0, };
	int global_node_diff[NR_VM_NODE_STAT_ITEMS] = { 0, };
	int changes = 0;

	for_each_populated_zone(zone) {
		struct per_cpu_pageset __percpu *p = zone->pageset;

		for (i = 0; i < NR_VM_ZONE_STAT_ITEMS; i++) {
			int v;

			v = this_cpu_xchg(p->vm_stat_diff[i], 0);
			if (v) {

				atomic_long_add(v, &zone->vm_stat[i]);
				global_zone_diff[i] += v;
#ifdef CONFIG_NUMA
				/* 3 seconds idle till flush */
				__this_cpu_write(p->expire, 3);
#endif
			}
		}
#ifdef CONFIG_NUMA
		if (do_pagesets) {
			cond_resched();
			/*
                         * Deal with draining the remote pageset of this
                         * processor
                         *
                         * Check if there are pages remaining in this pageset
                         * if not then there is nothing to expire.
                         */
			if (!__this_cpu_read(p->expire) ||
			       !__this_cpu_read(p->pcp.count))
				continue;

			/*
                         * We never drain zones local to this processor.
                         */
			if (zone_to_nid(zone) == numa_node_id()) {
				__this_cpu_write(p->expire, 0);
				continue;
			}

			if (__this_cpu_dec_return(p->expire))
				continue;

			if (__this_cpu_read(p->pcp.count)) {
				drain_zone_pages(zone, this_cpu_ptr(&p->pcp));
				changes++;
			}
		}
#endif
	}

	for_each_online_pgdat(pgdat) {
		struct per_cpu_nodestat __percpu *p = pgdat->per_cpu_nodestats;

		for (i = 0; i < NR_VM_NODE_STAT_ITEMS; i++) {
			int v;

			v = this_cpu_xchg(p->vm_node_stat_diff[i], 0);
			if (v) {
				atomic_long_add(v, &pgdat->vm_stat[i]);
				global_node_diff[i] += v;
			}
		}
	}

	changes += fold_diff(global_zone_diff, global_node_diff);
	return changes;
}

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/*
 * Fold the data for an offline cpu into the global array.
 * There cannot be any access by the offline cpu and therefore
 * synchronization is simplified.
 */


void cpu_vm_stats_fold(int cpu)
{
	struct pglist_data *pgdat;
	struct zone *zone;
	int i;
	int global_zone_diff[NR_VM_ZONE_STAT_ITEMS] = { 0, };
	int global_node_diff[NR_VM_NODE_STAT_ITEMS] = { 0, };

	for_each_populated_zone(zone) {
		struct per_cpu_pageset *p;

		p = per_cpu_ptr(zone->pageset, cpu);

		for (i = 0; i < NR_VM_ZONE_STAT_ITEMS; i++)
			if (p->vm_stat_diff[i]) {
				int v;

				v = p->vm_stat_diff[i];
				p->vm_stat_diff[i] = 0;
				atomic_long_add(v, &zone->vm_stat[i]);
				global_zone_diff[