Quelle vmstat.c Sprache: C

// SPDX-License-Identifier: GPL-2.0-only
/*
*  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 <cl@gentwo.org>
*  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_owner.h>
#include <linux/sched/isolation.h>

#include "internal.h"

#ifdef CONFIG_PROC_FS
#ifdef CONFIG_NUMA
#define ENABLE_NUMA_STAT 1
static int sysctl_vm_numa_stat = ENABLE_NUMA_STAT;

/* zero numa counters within a zone */
static void zero_zone_numa_counters(struct zone *zone)
{
int item, cpu;

for (item = 0; item < NR_VM_NUMA_EVENT_ITEMS; item++) {
  atomic_long_set(&zone->vm_numa_event[item], 0);
  for_each_online_cpu(cpu) {
   per_cpu_ptr(zone->per_cpu_zonestats, cpu)->vm_numa_event[item]
      = 0;
  }
}
}

/* zero numa counters of all the populated zones */
static void zero_zones_numa_counters(void)
{
struct zone *zone;

for_each_populated_zone(zone)
  zero_zone_numa_counters(zone);
}

/* zero global numa counters */
static void zero_global_numa_counters(void)
{
int item;

for (item = 0; item < NR_VM_NUMA_EVENT_ITEMS; item++)
  atomic_long_set(&vm_numa_event[item], 0);
}

static void invalid_numa_statistics(void)
{
zero_zones_numa_counters();
zero_global_numa_counters();
}

static DEFINE_MUTEX(vm_numa_stat_lock);

static int sysctl_vm_numa_stat_handler(const struct ctl_table *table, int write,
  void *buffer, size_t *length, loff_t *ppos)
{
int ret, oldval;

mutex_lock(&vm_numa_stat_lock);
if (write)
  oldval = sysctl_vm_numa_stat;
ret = proc_dointvec_minmax(table, write, buffer, length, ppos);
if (ret || !write)
  goto out;

if (oldval == sysctl_vm_numa_stat)
  goto out;
else if (sysctl_vm_numa_stat == ENABLE_NUMA_STAT) {
  static_branch_enable(&vm_numa_stat_key);
  pr_info("enable numa statistics\n");
} else {
  static_branch_disable(&vm_numa_stat_key);
  invalid_numa_statistics();
  pr_info("disable numa statistics, and clear numa counters\n");
}

out:
mutex_unlock(&vm_numa_stat_lock);
return ret;
}
#endif
#endif /* CONFIG_PROC_FS */

#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];
}
}

/*
* 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)
{
cpus_read_lock();
sum_vm_events(ret);
cpus_read_unlock();
}
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;
}
}

#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;
atomic_long_t vm_numa_event[NR_VM_NUMA_EVENT_ITEMS] __cacheline_aligned_in_smp;
EXPORT_SYMBOL(vm_zone_stat);
EXPORT_SYMBOL(vm_node_stat);

#ifdef CONFIG_NUMA
static void fold_vm_zone_numa_events(struct zone *zone)
{
unsigned long zone_numa_events[NR_VM_NUMA_EVENT_ITEMS] = { 0, };
int cpu;
enum numa_stat_item item;

for_each_online_cpu(cpu) {
  struct per_cpu_zonestat *pzstats;

  pzstats = per_cpu_ptr(zone->per_cpu_zonestats, cpu);
  for (item = 0; item < NR_VM_NUMA_EVENT_ITEMS; item++)
   zone_numa_events[item] += xchg(&pzstats->vm_numa_event[item], 0);
}

for (item = 0; item < NR_VM_NUMA_EVENT_ITEMS; item++)
  zone_numa_event_add(zone_numa_events[item], zone, item);
}

void fold_vm_numa_events(void)
{
struct zone *zone;

for_each_populated_zone(zone)
  fold_vm_zone_numa_events(zone);
}
#endif

#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;
}

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(zone) >> (27 - PAGE_SHIFT);

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

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

return threshold;
}

/*
* 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->per_cpu_zonestats, 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;
}
}

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->per_cpu_zonestats, cpu)->stat_threshold
       = threshold;
}
}

/*
* 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_zonestat __percpu *pcp = zone->per_cpu_zonestats;
s8 __percpu *p = pcp->vm_stat_diff + item;
long x;
long t;

/*
* Accurate vmstat updates require a RMW. On !PREEMPT_RT kernels,
* atomicity is provided by IRQs being disabled -- either explicitly
* or via local_lock_irq. On PREEMPT_RT, local_lock_irq only disables
* CPU migrations and preemption potentially corrupts a counter so
* disable preemption.
*/
preempt_disable_nested();

x = delta + __this_cpu_read(*p);

t = __this_cpu_read(pcp->stat_threshold);

if (unlikely(abs(x) > t)) {
  zone_page_state_add(x, zone, item);
  x = 0;
}
__this_cpu_write(*p, x);

preempt_enable_nested();
}
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;

if (vmstat_item_in_bytes(item)) {
  /*
* Only cgroups use subpage accounting right now; at
* the global level, these items still change in
* multiples of whole pages. Store them as pages
* internally to keep the per-cpu counters compact.
*/
  VM_WARN_ON_ONCE(delta & (PAGE_SIZE - 1));
  delta >>= PAGE_SHIFT;
}

/* See __mod_node_page_state */
preempt_disable_nested();

x = delta + __this_cpu_read(*p);

t = __this_cpu_read(pcp->stat_threshold);

if (unlikely(abs(x) > t)) {
  node_page_state_add(x, pgdat, item);
  x = 0;
}
__this_cpu_write(*p, x);

preempt_enable_nested();
}
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_zonestat __percpu *pcp = zone->per_cpu_zonestats;
s8 __percpu *p = pcp->vm_stat_diff + item;
s8 v, t;

/* See __mod_node_page_state */
preempt_disable_nested();

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);
}

preempt_enable_nested();
}

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;

VM_WARN_ON_ONCE(vmstat_item_in_bytes(item));

/* See __mod_node_page_state */
preempt_disable_nested();

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);
}

preempt_enable_nested();
}

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

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

/* See __mod_node_page_state */
preempt_disable_nested();

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);
}

preempt_enable_nested();
}

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;

VM_WARN_ON_ONCE(vmstat_item_in_bytes(item));

/* See __mod_node_page_state */
preempt_disable_nested();

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);
}

preempt_enable_nested();
}

void __dec_zone_page_state(struct page *page, enum zone_stat_item item)
{
__dec_zone_state(page_zone(page), item);
}
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);
}
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_zonestat __percpu *pcp = zone->per_cpu_zonestats;
s8 __percpu *p = pcp->vm_stat_diff + item;
long n, t, z;
s8 o;

o = this_cpu_read(*p);
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);

  n = delta + (long)o;

  if (abs(n) > t) {
   int os = overstep_mode * (t >> 1) ;

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

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

void mod_zone_page_state(struct zone *zone, enum zone_stat_item item,
    long delta)
{
mod_zone_state(zone, item, delta, 0);
}
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);
}
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);
}
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 n, t, z;
s8 o;

if (vmstat_item_in_bytes(item)) {
  /*
* Only cgroups use subpage accounting right now; at
* the global level, these items still change in
* multiples of whole pages. Store them as pages
* internally to keep the per-cpu counters compact.
*/
  VM_WARN_ON_ONCE(delta & (PAGE_SIZE - 1));
  delta >>= PAGE_SHIFT;
}

o = this_cpu_read(*p);
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);

  n = delta + (long)o;

  if (abs(n) > t) {
   int os = overstep_mode * (t >> 1) ;

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

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

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

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

/*
* 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_zonestat __percpu *pzstats = zone->per_cpu_zonestats;
  struct per_cpu_pages __percpu *pcp = zone->per_cpu_pageset;

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

   v = this_cpu_xchg(pzstats->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(pcp->expire, 3);
#endif
   }
  }

  if (do_pagesets) {
   cond_resched();

   changes += decay_pcp_high(zone, this_cpu_ptr(pcp));
#ifdef CONFIG_NUMA
   /*
* 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(pcp->expire) ||
          !__this_cpu_read(pcp->count))
    continue;

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

   if (__this_cpu_dec_return(pcp->expire)) {
    changes++;
    continue;
   }

   if (__this_cpu_read(pcp->count)) {
    drain_zone_pages(zone, this_cpu_ptr(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;
}

/*
* 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_zonestat *pzstats;

  pzstats = per_cpu_ptr(zone->per_cpu_zonestats, cpu);

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

    v = pzstats->vm_stat_diff[i];
    pzstats->vm_stat_diff[i] = 0;
    atomic_long_add(v, &zone->vm_stat[i]);
    global_zone_diff[i] += v;
   }
  }
#ifdef CONFIG_NUMA
  for (i = 0; i < NR_VM_NUMA_EVENT_ITEMS; i++) {
   if (pzstats->vm_numa_event[i]) {
    unsigned long v;

    v = pzstats->vm_numa_event[i];
    pzstats->vm_numa_event[i] = 0;
    zone_numa_event_add(v, zone, i);
   }
  }
#endif
}

for_each_online_pgdat(pgdat) {
  struct per_cpu_nodestat *p;

  p = per_cpu_ptr(pgdat->per_cpu_nodestats, cpu);

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

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

fold_diff(global_zone_diff, global_node_diff);
}

/*
* this is only called if !populated_zone(zone), which implies no other users of
* pset->vm_stat_diff[] exist.
*/
void drain_zonestat(struct zone *zone, struct per_cpu_zonestat *pzstats)
{
unsigned long v;
int i;

for (i = 0; i < NR_VM_ZONE_STAT_ITEMS; i++) {
  if (pzstats->vm_stat_diff[i]) {
   v = pzstats->vm_stat_diff[i];
   pzstats->vm_stat_diff[i] = 0;
   zone_page_state_add(v, zone, i);
  }
}

#ifdef CONFIG_NUMA
for (i = 0; i < NR_VM_NUMA_EVENT_ITEMS; i++) {
  if (pzstats->vm_numa_event[i]) {
   v = pzstats->vm_numa_event[i];
   pzstats->vm_numa_event[i] = 0;
   zone_numa_event_add(v, zone, i);
  }
}
#endif
}
#endif

#ifdef CONFIG_NUMA
/*
* Determine the per node value of a stat item. This function
* is called frequently in a NUMA machine, so try to be as
* frugal as possible.
*/
unsigned long sum_zone_node_page_state(int node,
     enum zone_stat_item item)
{
struct zone *zones = NODE_DATA(node)->node_zones;
int i;
unsigned long count = 0;

for (i = 0; i < MAX_NR_ZONES; i++)
  count += zone_page_state(zones + i, item);

return count;
}

/* Determine the per node value of a numa stat item. */
unsigned long sum_zone_numa_event_state(int node,
     enum numa_stat_item item)
{
struct zone *zones = NODE_DATA(node)->node_zones;
unsigned long count = 0;
int i;

for (i = 0; i < MAX_NR_ZONES; i++)
  count += zone_numa_event_state(zones + i, item);

return count;
}

/*
* Determine the per node value of a stat item.
*/
unsigned long node_page_state_pages(struct pglist_data *pgdat,
        enum node_stat_item item)
{
long x = atomic_long_read(&pgdat->vm_stat[item]);
#ifdef CONFIG_SMP
if (x < 0)
  x = 0;
#endif
return x;
}

unsigned long node_page_state(struct pglist_data *pgdat,
         enum node_stat_item item)
{
VM_WARN_ON_ONCE(vmstat_item_in_bytes(item));

return node_page_state_pages(pgdat, item);
}
#endif

/*
* Count number of pages "struct page" and "struct page_ext" consume.
* nr_memmap_boot_pages: # of pages allocated by boot allocator
* nr_memmap_pages: # of pages that were allocated by buddy allocator
*/
static atomic_long_t nr_memmap_boot_pages = ATOMIC_LONG_INIT(0);
static atomic_long_t nr_memmap_pages = ATOMIC_LONG_INIT(0);

void memmap_boot_pages_add(long delta)
{
atomic_long_add(delta, &nr_memmap_boot_pages);
}

void memmap_pages_add(long delta)
{
atomic_long_add(delta, &nr_memmap_pages);
}

#ifdef CONFIG_COMPACTION

struct contig_page_info {
unsigned long free_pages;
unsigned long free_blocks_total;
unsigned long free_blocks_suitable;
};

/*
* Calculate the number of free pages in a zone, how many contiguous
* pages are free and how many are large enough to satisfy an allocation of
* the target size. Note that this function makes no attempt to estimate
* how many suitable free blocks there *might* be if MOVABLE pages were
* migrated. Calculating that is possible, but expensive and can be
* figured out from userspace
*/
static void fill_contig_page_info(struct zone *zone,
    unsigned int suitable_order,
    struct contig_page_info *info)
{
unsigned int order;

info->free_pages = 0;
info->free_blocks_total = 0;
info->free_blocks_suitable = 0;

for (order = 0; order < NR_PAGE_ORDERS; order++) {
  unsigned long blocks;

  /*
* Count number of free blocks.
*
* Access to nr_free is lockless as nr_free is used only for
* diagnostic purposes. Use data_race to avoid KCSAN warning.
*/
  blocks = data_race(zone->free_area[order].nr_free);
  info->free_blocks_total += blocks;

  /* Count free base pages */
  info->free_pages += blocks << order;

  /* Count the suitable free blocks */
  if (order >= suitable_order)
   info->free_blocks_suitable += blocks <<
      (order - suitable_order);
}
}

/*
* A fragmentation index only makes sense if an allocation of a requested
* size would fail. If that is true, the fragmentation index indicates
* whether external fragmentation or a lack of memory was the problem.
* The value can be used to determine if page reclaim or compaction
* should be used
*/
static int __fragmentation_index(unsigned int order, struct contig_page_info *info)
{
unsigned long requested = 1UL << order;

if (WARN_ON_ONCE(order > MAX_PAGE_ORDER))
  return 0;

if (!info->free_blocks_total)
  return 0;

/* Fragmentation index only makes sense when a request would fail */
if (info->free_blocks_suitable)
  return -1000;

/*
* Index is between 0 and 1 so return within 3 decimal places
*
* 0 => allocation would fail due to lack of memory
* 1 => allocation would fail due to fragmentation
*/
return 1000 - div_u64( (1000+(div_u64(info->free_pages * 1000ULL, requested))), info->free_blocks_total);
}

/*
* Calculates external fragmentation within a zone wrt the given order.
* It is defined as the percentage of pages found in blocks of size
* less than 1 << order. It returns values in range [0, 100].
*/
unsigned int extfrag_for_order(struct zone *zone, unsigned int order)
{
struct contig_page_info info;

fill_contig_page_info(zone, order, &info);
if (info.free_pages == 0)
  return 0;

return div_u64((info.free_pages -
   (info.free_blocks_suitable << order)) * 100,
   info.free_pages);
}

/* Same as __fragmentation index but allocs contig_page_info on stack */
int fragmentation_index(struct zone *zone, unsigned int order)
{
struct contig_page_info info;

fill_contig_page_info(zone, order, &info);
return __fragmentation_index(order, &info);
}
#endif

#if defined(CONFIG_PROC_FS) || defined(CONFIG_SYSFS) || \
    defined(CONFIG_NUMA) || defined(CONFIG_MEMCG)
#ifdef CONFIG_ZONE_DMA
#define TEXT_FOR_DMA(xx, yy) [xx##_DMA] = yy "_dma",
#else
#define TEXT_FOR_DMA(xx, yy)
#endif

#ifdef CONFIG_ZONE_DMA32
#define TEXT_FOR_DMA32(xx, yy) [xx##_DMA32] = yy "_dma32",
#else
#define TEXT_FOR_DMA32(xx, yy)
#endif

#ifdef CONFIG_HIGHMEM
#define TEXT_FOR_HIGHMEM(xx, yy) [xx##_HIGH] = yy "_high",
#else
#define TEXT_FOR_HIGHMEM(xx, yy)
#endif

#ifdef CONFIG_ZONE_DEVICE
#define TEXT_FOR_DEVICE(xx, yy) [xx##_DEVICE] = yy "_device",
#else
#define TEXT_FOR_DEVICE(xx, yy)
#endif

#define TEXTS_FOR_ZONES(xx, yy)   \
TEXT_FOR_DMA(xx, yy)   \
TEXT_FOR_DMA32(xx, yy)   \
[xx##_NORMAL] = yy "_normal",  \
TEXT_FOR_HIGHMEM(xx, yy)  \
[xx##_MOVABLE] = yy "_movable",  \
TEXT_FOR_DEVICE(xx, yy)

const char * const vmstat_text[] = {
/* enum zone_stat_item counters */
#define I(x) (x)
[I(NR_FREE_PAGES)]   = "nr_free_pages",
[I(NR_FREE_PAGES_BLOCKS)]  = "nr_free_pages_blocks",
[I(NR_ZONE_INACTIVE_ANON)]  = "nr_zone_inactive_anon",
[I(NR_ZONE_ACTIVE_ANON)]  = "nr_zone_active_anon",
[I(NR_ZONE_INACTIVE_FILE)]  = "nr_zone_inactive_file",
[I(NR_ZONE_ACTIVE_FILE)]  = "nr_zone_active_file",
[I(NR_ZONE_UNEVICTABLE)]  = "nr_zone_unevictable",
[I(NR_ZONE_WRITE_PENDING)]  = "nr_zone_write_pending",
[I(NR_MLOCK)]    = "nr_mlock",
#if IS_ENABLED(CONFIG_ZSMALLOC)
[I(NR_ZSPAGES)]    = "nr_zspages",
#endif
[I(NR_FREE_CMA_PAGES)]   = "nr_free_cma",
#ifdef CONFIG_UNACCEPTED_MEMORY
[I(NR_UNACCEPTED)]   = "nr_unaccepted",
#endif
#undef I

/* enum numa_stat_item counters */
#define I(x) (NR_VM_ZONE_STAT_ITEMS + x)
#ifdef CONFIG_NUMA
[I(NUMA_HIT)]    = "numa_hit",
[I(NUMA_MISS)]    = "numa_miss",
[I(NUMA_FOREIGN)]   = "numa_foreign",
[I(NUMA_INTERLEAVE_HIT)]  = "numa_interleave",
[I(NUMA_LOCAL)]    = "numa_local",
[I(NUMA_OTHER)]    = "numa_other",
#endif
#undef I

/* enum node_stat_item counters */
#define I(x) (NR_VM_ZONE_STAT_ITEMS + NR_VM_NUMA_EVENT_ITEMS + x)
[I(NR_INACTIVE_ANON)]   = "nr_inactive_anon",
[I(NR_ACTIVE_ANON)]   = "nr_active_anon",
[I(NR_INACTIVE_FILE)]   = "nr_inactive_file",
[I(NR_ACTIVE_FILE)]   = "nr_active_file",
[I(NR_UNEVICTABLE)]   = "nr_unevictable",
[I(NR_SLAB_RECLAIMABLE_B)]  = "nr_slab_reclaimable",
[I(NR_SLAB_UNRECLAIMABLE_B)]  = "nr_slab_unreclaimable",
[I(NR_ISOLATED_ANON)]   = "nr_isolated_anon",
[I(NR_ISOLATED_FILE)]   = "nr_isolated_file",
[I(WORKINGSET_NODES)]   = "workingset_nodes",
[I(WORKINGSET_REFAULT_ANON)]  = "workingset_refault_anon",
[I(WORKINGSET_REFAULT_FILE)]  = "workingset_refault_file",
[I(WORKINGSET_ACTIVATE_ANON)]  = "workingset_activate_anon",
[I(WORKINGSET_ACTIVATE_FILE)]  = "workingset_activate_file",
[I(WORKINGSET_RESTORE_ANON)]  = "workingset_restore_anon",
[I(WORKINGSET_RESTORE_FILE)]  = "workingset_restore_file",
[I(WORKINGSET_NODERECLAIM)]  = "workingset_nodereclaim",
[I(NR_ANON_MAPPED)]   = "nr_anon_pages",
[I(NR_FILE_MAPPED)]   = "nr_mapped",
[I(NR_FILE_PAGES)]   = "nr_file_pages",
[I(NR_FILE_DIRTY)]   = "nr_dirty",
[I(NR_WRITEBACK)]   = "nr_writeback",
[I(NR_SHMEM)]    = "nr_shmem",
[I(NR_SHMEM_THPS)]   = "nr_shmem_hugepages",
[I(NR_SHMEM_PMDMAPPED)]   = "nr_shmem_pmdmapped",
[I(NR_FILE_THPS)]   = "nr_file_hugepages",
[I(NR_FILE_PMDMAPPED)]   = "nr_file_pmdmapped",
[I(NR_ANON_THPS)]   = "nr_anon_transparent_hugepages",
[I(NR_VMSCAN_WRITE)]   = "nr_vmscan_write",
[I(NR_VMSCAN_IMMEDIATE)]  = "nr_vmscan_immediate_reclaim",
[I(NR_DIRTIED)]    = "nr_dirtied",
[I(NR_WRITTEN)]    = "nr_written",
[I(NR_THROTTLED_WRITTEN)]  = "nr_throttled_written",
[I(NR_KERNEL_MISC_RECLAIMABLE)]  = "nr_kernel_misc_reclaimable",
[I(NR_FOLL_PIN_ACQUIRED)]  = "nr_foll_pin_acquired",
[I(NR_FOLL_PIN_RELEASED)]  = "nr_foll_pin_released",
[I(NR_KERNEL_STACK_KB)]   = "nr_kernel_stack",
#if IS_ENABLED(CONFIG_SHADOW_CALL_STACK)
[I(NR_KERNEL_SCS_KB)]   = "nr_shadow_call_stack",
#endif
[I(NR_PAGETABLE)]   = "nr_page_table_pages",
[I(NR_SECONDARY_PAGETABLE)]  = "nr_sec_page_table_pages",
#ifdef CONFIG_IOMMU_SUPPORT
[I(NR_IOMMU_PAGES)]   = "nr_iommu_pages",
#endif
#ifdef CONFIG_SWAP
[I(NR_SWAPCACHE)]   = "nr_swapcached",
#endif
#ifdef CONFIG_NUMA_BALANCING
[I(PGPROMOTE_SUCCESS)]   = "pgpromote_success",
[I(PGPROMOTE_CANDIDATE)]  = "pgpromote_candidate",
#endif
[I(PGDEMOTE_KSWAPD)]   = "pgdemote_kswapd",
[I(PGDEMOTE_DIRECT)]   = "pgdemote_direct",
[I(PGDEMOTE_KHUGEPAGED)]  = "pgdemote_khugepaged",
[I(PGDEMOTE_PROACTIVE)]   = "pgdemote_proactive",
#ifdef CONFIG_HUGETLB_PAGE
[I(NR_HUGETLB)]    = "nr_hugetlb",
#endif
[I(NR_BALLOON_PAGES)]   = "nr_balloon_pages",
#undef I

/* system-wide enum vm_stat_item counters */
#define I(x) (NR_VM_ZONE_STAT_ITEMS + NR_VM_NUMA_EVENT_ITEMS + \
      NR_VM_NODE_STAT_ITEMS + x)
[I(NR_DIRTY_THRESHOLD)]   = "nr_dirty_threshold",
[I(NR_DIRTY_BG_THRESHOLD)]  = "nr_dirty_background_threshold",
[I(NR_MEMMAP_PAGES)]   = "nr_memmap_pages",
[I(NR_MEMMAP_BOOT_PAGES)]  = "nr_memmap_boot_pages",
#undef I

#if defined(CONFIG_VM_EVENT_COUNTERS)
/* enum vm_event_item counters */
#define I(x) (NR_VM_ZONE_STAT_ITEMS + NR_VM_NUMA_EVENT_ITEMS + \
      NR_VM_NODE_STAT_ITEMS + NR_VM_STAT_ITEMS + x)

[I(PGPGIN)]    = "pgpgin",
[I(PGPGOUT)]    = "pgpgout",
[I(PSWPIN)]    = "pswpin",
[I(PSWPOUT)]    = "pswpout",

#define OFF (NR_VM_ZONE_STAT_ITEMS + NR_VM_NUMA_EVENT_ITEMS + \
      NR_VM_NODE_STAT_ITEMS + NR_VM_STAT_ITEMS)
TEXTS_FOR_ZONES(OFF+PGALLOC, "pgalloc")
TEXTS_FOR_ZONES(OFF+ALLOCSTALL, "allocstall")
TEXTS_FOR_ZONES(OFF+PGSCAN_SKIP, "pgskip")
#undef OFF

[I(PGFREE)]    = "pgfree",
[I(PGACTIVATE)]    = "pgactivate",
[I(PGDEACTIVATE)]   = "pgdeactivate",
[I(PGLAZYFREE)]    = "pglazyfree",

[I(PGFAULT)]    = "pgfault",
[I(PGMAJFAULT)]    = "pgmajfault",
[I(PGLAZYFREED)]   = "pglazyfreed",

[I(PGREFILL)]    = "pgrefill",
[I(PGREUSE)]    = "pgreuse",
[I(PGSTEAL_KSWAPD)]   = "pgsteal_kswapd",
[I(PGSTEAL_DIRECT)]   = "pgsteal_direct",
[I(PGSTEAL_KHUGEPAGED)]   = "pgsteal_khugepaged",
[I(PGSTEAL_PROACTIVE)]   = "pgsteal_proactive",
[I(PGSCAN_KSWAPD)]   = "pgscan_kswapd",
[I(PGSCAN_DIRECT)]   = "pgscan_direct",
[I(PGSCAN_KHUGEPAGED)]   = "pgscan_khugepaged",
[I(PGSCAN_PROACTIVE)]   = "pgscan_proactive",
[I(PGSCAN_DIRECT_THROTTLE)]  = "pgscan_direct_throttle",
[I(PGSCAN_ANON)]   = "pgscan_anon",
[I(PGSCAN_FILE)]   = "pgscan_file",
[I(PGSTEAL_ANON)]   = "pgsteal_anon",
[I(PGSTEAL_FILE)]   = "pgsteal_file",

#ifdef CONFIG_NUMA
[I(PGSCAN_ZONE_RECLAIM_SUCCESS)] = "zone_reclaim_success",
[I(PGSCAN_ZONE_RECLAIM_FAILED)]  = "zone_reclaim_failed",
#endif
[I(PGINODESTEAL)]   = "pginodesteal",
[I(SLABS_SCANNED)]   = "slabs_scanned",
[I(KSWAPD_INODESTEAL)]   = "kswapd_inodesteal",
[I(KSWAPD_LOW_WMARK_HIT_QUICKLY)] = "kswapd_low_wmark_hit_quickly",
[I(KSWAPD_HIGH_WMARK_HIT_QUICKLY)] = "kswapd_high_wmark_hit_quickly",
[I(PAGEOUTRUN)]    = "pageoutrun",

[I(PGROTATED)]    = "pgrotated",

[I(DROP_PAGECACHE)]   = "drop_pagecache",
[I(DROP_SLAB)]    = "drop_slab",
[I(OOM_KILL)]    = "oom_kill",

#ifdef CONFIG_NUMA_BALANCING
[I(NUMA_PTE_UPDATES)]   = "numa_pte_updates",
[I(NUMA_HUGE_PTE_UPDATES)]  = "numa_huge_pte_updates",
[I(NUMA_HINT_FAULTS)]   = "numa_hint_faults",
[I(NUMA_HINT_FAULTS_LOCAL)]  = "numa_hint_faults_local",
[I(NUMA_PAGE_MIGRATE)]   = "numa_pages_migrated",
#endif
#ifdef CONFIG_MIGRATION
[I(PGMIGRATE_SUCCESS)]   = "pgmigrate_success",
[I(PGMIGRATE_FAIL)]   = "pgmigrate_fail",
[I(THP_MIGRATION_SUCCESS)]  = "thp_migration_success",
[I(THP_MIGRATION_FAIL)]   = "thp_migration_fail",
[I(THP_MIGRATION_SPLIT)]  = "thp_migration_split",
#endif
#ifdef CONFIG_COMPACTION
[I(COMPACTMIGRATE_SCANNED)]  = "compact_migrate_scanned",
[I(COMPACTFREE_SCANNED)]  = "compact_free_scanned",
[I(COMPACTISOLATED)]   = "compact_isolated",
[I(COMPACTSTALL)]   = "compact_stall",
[I(COMPACTFAIL)]   = "compact_fail",
[I(COMPACTSUCCESS)]   = "compact_success",
[I(KCOMPACTD_WAKE)]   = "compact_daemon_wake",
[I(KCOMPACTD_MIGRATE_SCANNED)]  = "compact_daemon_migrate_scanned",
[I(KCOMPACTD_FREE_SCANNED)]  = "compact_daemon_free_scanned",
#endif

#ifdef CONFIG_HUGETLB_PAGE
[I(HTLB_BUDDY_PGALLOC)]   = "htlb_buddy_alloc_success",
[I(HTLB_BUDDY_PGALLOC_FAIL)]  = "htlb_buddy_alloc_fail",
#endif
#ifdef CONFIG_CMA
[I(CMA_ALLOC_SUCCESS)]   = "cma_alloc_success",
[I(CMA_ALLOC_FAIL)]   = "cma_alloc_fail",
#endif
[I(UNEVICTABLE_PGCULLED)]  = "unevictable_pgs_culled",
[I(UNEVICTABLE_PGSCANNED)]  = "unevictable_pgs_scanned",
[I(UNEVICTABLE_PGRESCUED)]  = "unevictable_pgs_rescued",
[I(UNEVICTABLE_PGMLOCKED)]  = "unevictable_pgs_mlocked",
[I(UNEVICTABLE_PGMUNLOCKED)]  = "unevictable_pgs_munlocked",
[I(UNEVICTABLE_PGCLEARED)]  = "unevictable_pgs_cleared",
[I(UNEVICTABLE_PGSTRANDED)]  = "unevictable_pgs_stranded",

#ifdef CONFIG_TRANSPARENT_HUGEPAGE
[I(THP_FAULT_ALLOC)]   = "thp_fault_alloc",
[I(THP_FAULT_FALLBACK)]   = "thp_fault_fallback",
[I(THP_FAULT_FALLBACK_CHARGE)]  = "thp_fault_fallback_charge",
[I(THP_COLLAPSE_ALLOC)]   = "thp_collapse_alloc",
[I(THP_COLLAPSE_ALLOC_FAILED)]  = "thp_collapse_alloc_failed",
[I(THP_FILE_ALLOC)]   = "thp_file_alloc",
[I(THP_FILE_FALLBACK)]   = "thp_file_fallback",
[I(THP_FILE_FALLBACK_CHARGE)]  = "thp_file_fallback_charge",
[I(THP_FILE_MAPPED)]   = "thp_file_mapped",
[I(THP_SPLIT_PAGE)]   = "thp_split_page",
[I(THP_SPLIT_PAGE_FAILED)]  = "thp_split_page_failed",
[I(THP_DEFERRED_SPLIT_PAGE)]  = "thp_deferred_split_page",
[I(THP_UNDERUSED_SPLIT_PAGE)]  = "thp_underused_split_page",
[I(THP_SPLIT_PMD)]   = "thp_split_pmd",
[I(THP_SCAN_EXCEED_NONE_PTE)]  = "thp_scan_exceed_none_pte",
[I(THP_SCAN_EXCEED_SWAP_PTE)]  = "thp_scan_exceed_swap_pte",
[I(THP_SCAN_EXCEED_SHARED_PTE)]  = "thp_scan_exceed_share_pte",
#ifdef CONFIG_HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD
[I(THP_SPLIT_PUD)]   = "thp_split_pud",
#endif
[I(THP_ZERO_PAGE_ALLOC)]  = "thp_zero_page_alloc",
[I(THP_ZERO_PAGE_ALLOC_FAILED)]  = "thp_zero_page_alloc_failed",
[I(THP_SWPOUT)]    = "thp_swpout",
[I(THP_SWPOUT_FALLBACK)]  = "thp_swpout_fallback",
#endif
#ifdef CONFIG_MEMORY_BALLOON
[I(BALLOON_INFLATE)]   = "balloon_inflate",
[I(BALLOON_DEFLATE)]   = "balloon_deflate",
#ifdef CONFIG_BALLOON_COMPACTION
[I(BALLOON_MIGRATE)]   = "balloon_migrate",
#endif
#endif /* CONFIG_MEMORY_BALLOON */
#ifdef CONFIG_DEBUG_TLBFLUSH
[I(NR_TLB_REMOTE_FLUSH)]  = "nr_tlb_remote_flush",
[I(NR_TLB_REMOTE_FLUSH_RECEIVED)] = "nr_tlb_remote_flush_received",
[I(NR_TLB_LOCAL_FLUSH_ALL)]  = "nr_tlb_local_flush_all",
[I(NR_TLB_LOCAL_FLUSH_ONE)]  = "nr_tlb_local_flush_one",
#endif /* CONFIG_DEBUG_TLBFLUSH */

#ifdef CONFIG_SWAP
[I(SWAP_RA)]    = "swap_ra",
[I(SWAP_RA_HIT)]   = "swap_ra_hit",
[I(SWPIN_ZERO)]    = "swpin_zero",
[I(SWPOUT_ZERO)]   = "swpout_zero",
#ifdef CONFIG_KSM
[I(KSM_SWPIN_COPY)]   = "ksm_swpin_copy",
#endif
#endif
#ifdef CONFIG_KSM
[I(COW_KSM)]    = "cow_ksm",
#endif
#ifdef CONFIG_ZSWAP
[I(ZSWPIN)]    = "zswpin",
[I(ZSWPOUT)]    = "zswpout",
[I(ZSWPWB)]    = "zswpwb",
#endif
#ifdef CONFIG_X86
[I(DIRECT_MAP_LEVEL2_SPLIT)]  = "direct_map_level2_splits",
[I(DIRECT_MAP_LEVEL3_SPLIT)]  = "direct_map_level3_splits",
[I(DIRECT_MAP_LEVEL2_COLLAPSE)]  = "direct_map_level2_collapses",
[I(DIRECT_MAP_LEVEL3_COLLAPSE)]  = "direct_map_level3_collapses",
#endif
#ifdef CONFIG_PER_VMA_LOCK_STATS
[I(VMA_LOCK_SUCCESS)]   = "vma_lock_success",
[I(VMA_LOCK_ABORT)]   = "vma_lock_abort",
[I(VMA_LOCK_RETRY)]   = "vma_lock_retry",
[I(VMA_LOCK_MISS)]   = "vma_lock_miss",
#endif
#ifdef CONFIG_DEBUG_STACK_USAGE
[I(KSTACK_1K)]    = "kstack_1k",
#if THREAD_SIZE > 1024
[I(KSTACK_2K)]    = "kstack_2k",
#endif
#if THREAD_SIZE > 2048
[I(KSTACK_4K)]    = "kstack_4k",
#endif
#if THREAD_SIZE > 4096
[I(KSTACK_8K)]    = "kstack_8k",
#endif
#if THREAD_SIZE > 8192
[I(KSTACK_16K)]    = "kstack_16k",
#endif
#if THREAD_SIZE > 16384
[I(KSTACK_32K)]    = "kstack_32k",
#endif
#if THREAD_SIZE > 32768
[I(KSTACK_64K)]    = "kstack_64k",
#endif
#if THREAD_SIZE > 65536
[I(KSTACK_REST)]   = "kstack_rest",
#endif
#endif
#undef I
#endif /* CONFIG_VM_EVENT_COUNTERS */
};
#endif /* CONFIG_PROC_FS || CONFIG_SYSFS || CONFIG_NUMA || CONFIG_MEMCG */

#if (defined(CONFIG_DEBUG_FS) && defined(CONFIG_COMPACTION)) || \
     defined(CONFIG_PROC_FS)
static void *frag_start(struct seq_file *m, loff_t *pos)
{
pg_data_t *pgdat;
loff_t node = *pos;

for (pgdat = first_online_pgdat();
      pgdat && node;
      pgdat = next_online_pgdat(pgdat))
  --node;

return pgdat;
}

static void *frag_next(struct seq_file *m, void *arg, loff_t *pos)
{
pg_data_t *pgdat = (pg_data_t *)arg;

(*pos)++;
return next_online_pgdat(pgdat);
}

static void frag_stop(struct seq_file *m, void *arg)
{
}

/*
* Walk zones in a node and print using a callback.
* If @assert_populated is true, only use callback for zones that are populated.
*/
static void walk_zones_in_node(struct seq_file *m, pg_data_t *pgdat,
  bool assert_populated, bool nolock,
  void (*print)(struct seq_file *m, pg_data_t *, struct zone *))
{
struct zone *zone;
struct zone *node_zones = pgdat->node_zones;
unsigned long flags;

for (zone = node_zones; zone - node_zones < MAX_NR_ZONES; ++zone) {
  if (assert_populated && !populated_zone(zone))
   continue;

  if (!nolock)
   spin_lock_irqsave(&zone->lock, flags);
  print(m, pgdat, zone);
  if (!nolock)
   spin_unlock_irqrestore(&zone->lock, flags);
}
}
#endif

#ifdef CONFIG_PROC_FS
static void frag_show_print(struct seq_file *m, pg_data_t *pgdat,
      struct zone *zone)
{
int order;

seq_printf(m, "Node %d, zone %8s ", pgdat->node_id, zone->name);
for (order = 0; order < NR_PAGE_ORDERS; ++order)
  /*
* Access to nr_free is lockless as nr_free is used only for
* printing purposes. Use data_race to avoid KCSAN warning.
*/
  seq_printf(m, "%6lu ", data_race(zone->free_area[order].nr_free));
seq_putc(m, '\n');
}

/*
* This walks the free areas for each zone.
*/
static int frag_show(struct seq_file *m, void *arg)
{
pg_data_t *pgdat = (pg_data_t *)arg;
walk_zones_in_node(m, pgdat, true, false, frag_show_print);
return 0;
}

static void pagetypeinfo_showfree_print(struct seq_file *m,
     pg_data_t *pgdat, struct zone *zone)
{
int order, mtype;

for (mtype = 0; mtype < MIGRATE_TYPES; mtype++) {
  seq_printf(m, "Node %4d, zone %8s, type %12s ",
     pgdat->node_id,
     zone->name,
     migratetype_names[mtype]);
  for (order = 0; order < NR_PAGE_ORDERS; ++order) {
   unsigned long freecount = 0;
   struct free_area *area;
   struct list_head *curr;
   bool overflow = false;

   area = &(zone->free_area[order]);

   list_for_each(curr, &area->free_list[mtype]) {
    /*
* Cap the free_list iteration because it might
* be really large and we are under a spinlock
* so a long time spent here could trigger a
* hard lockup detector. Anyway this is a
* debugging tool so knowing there is a handful
* of pages of this order should be more than
* sufficient.
*/
    if (++freecount >= 100000) {
     overflow = true;
     break;
    }
   }
   seq_printf(m, "%s%6lu ", overflow ? ">" : "", freecount);
   spin_unlock_irq(&zone->lock);
   cond_resched();
   spin_lock_irq(&zone->lock);
  }
  seq_putc(m, '\n');
}
}

/* Print out the free pages at each order for each migatetype */
static void pagetypeinfo_showfree(struct seq_file *m, void *arg)
{
int order;
pg_data_t *pgdat = (pg_data_t *)arg;

/* Print header */
seq_printf(m, "%-43s ", "Free pages count per migrate type at order");
for (order = 0; order < NR_PAGE_ORDERS; ++order)
  seq_printf(m, "%6d ", order);
seq_putc(m, '\n');

walk_zones_in_node(m, pgdat, true, false, pagetypeinfo_showfree_print);
}

static void pagetypeinfo_showblockcount_print(struct seq_file *m,
     pg_data_t *pgdat, struct zone *zone)
{
int mtype;
unsigned long pfn;
unsigned long start_pfn = zone->zone_start_pfn;
unsigned long end_pfn = zone_end_pfn(zone);
unsigned long count[MIGRATE_TYPES] = { 0, };

for (pfn = start_pfn; pfn < end_pfn; pfn += pageblock_nr_pages) {
  struct page *page;

  page = pfn_to_online_page(pfn);
  if (!page)
   continue;

  if (page_zone(page) != zone)
   continue;

  mtype = get_pageblock_migratetype(page);

  if (mtype < MIGRATE_TYPES)
   count[mtype]++;
}

/* Print counts */
seq_printf(m, "Node %d, zone %8s ", pgdat->node_id, zone->name);
for (mtype = 0; mtype < MIGRATE_TYPES; mtype++)
  seq_printf(m, "%12lu ", count[mtype]);
seq_putc(m, '\n');
}

/* Print out the number of pageblocks for each migratetype */
static void pagetypeinfo_showblockcount(struct seq_file *m, void *arg)
{
int mtype;
pg_data_t *pgdat = (pg_data_t *)arg;

seq_printf(m, "\n%-23s", "Number of blocks type ");
for (mtype = 0; mtype < MIGRATE_TYPES; mtype++)
  seq_printf(m, "%12s ", migratetype_names[mtype]);
seq_putc(m, '\n');
walk_zones_in_node(m, pgdat, true, false,
  pagetypeinfo_showblockcount_print);
}

/*
* Print out the number of pageblocks for each migratetype that contain pages
* of other types. This gives an indication of how well fallbacks are being
* contained by rmqueue_fallback(). It requires information from PAGE_OWNER
* to determine what is going on
*/
static void pagetypeinfo_showmixedcount(struct seq_file *m, pg_data_t *pgdat)
{
#ifdef CONFIG_PAGE_OWNER
int mtype;

if (!static_branch_unlikely(&page_owner_inited))
  return;

drain_all_pages(NULL);

seq_printf(m, "\n%-23s", "Number of mixed blocks ");
for (mtype = 0; mtype < MIGRATE_TYPES; mtype++)
  seq_printf(m, "%12s ", migratetype_names[mtype]);
seq_putc(m, '\n');

walk_zones_in_node(m, pgdat, true, true,
  pagetypeinfo_showmixedcount_print);
#endif /* CONFIG_PAGE_OWNER */
}

/*
* This prints out statistics in relation to grouping pages by mobility.
* It is expensive to collect so do not constantly read the file.
*/
static int pagetypeinfo_show(struct seq_file *m, void *arg)
{
pg_data_t *pgdat = (pg_data_t *)arg;

/* check memoryless node */
if (!node_state(pgdat->node_id, N_MEMORY))
  return 0;

seq_printf(m, "Page block order: %d\n", pageblock_order);
seq_printf(m, "Pages per block: %lu\n", pageblock_nr_pages);
seq_putc(m, '\n');
pagetypeinfo_showfree(m, pgdat);
pagetypeinfo_showblockcount(m, pgdat);
pagetypeinfo_showmixedcount(m, pgdat);

return 0;
}

static const struct seq_operations fragmentation_op = {
.start = frag_start,
.next = frag_next,
.stop = frag_stop,
.show = frag_show,
};

static const struct seq_operations pagetypeinfo_op = {
.start = frag_start,
.next = frag_next,
.stop = frag_stop,
.show = pagetypeinfo_show,
};

static bool is_zone_first_populated(pg_data_t *pgdat, struct zone *zone)
{
int zid;

for (zid = 0; zid < MAX_NR_ZONES; zid++) {
  struct zone *compare = &pgdat->node_zones[zid];

  if (populated_zone(compare))
   return zone == compare;
}

return false;
}

static void zoneinfo_show_print(struct seq_file *m, pg_data_t *pgdat,
       struct zone *zone)
{
int i;
seq_printf(m, "Node %d, zone %8s", pgdat->node_id, zone->name);
if (is_zone_first_populated(pgdat, zone)) {
  seq_printf(m, "\n per-node stats");
  for (i = 0; i < NR_VM_NODE_STAT_ITEMS; i++) {
   unsigned long pages = node_page_state_pages(pgdat, i);

   if (vmstat_item_print_in_thp(i))
    pages /= HPAGE_PMD_NR;
   seq_printf(m, "\n %-12s %lu", node_stat_name(i),
       pages);
  }
}
seq_printf(m,
     "\n pages free %lu"
     "\n boost %lu"
     "\n min %lu"
     "\n low %lu"
     "\n high %lu"
     "\n promo %lu"
     "\n spanned %lu"
     "\n present %lu"
     "\n managed %lu"
     "\n cma %lu",
     zone_page_state(zone, NR_FREE_PAGES),
     zone->watermark_boost,
     min_wmark_pages(zone),
     low_wmark_pages(zone),
     high_wmark_pages(zone),
     promo_wmark_pages(zone),
     zone->spanned_pages,
     zone->present_pages,
     zone_managed_pages(zone),
     zone_cma_pages(zone));

seq_printf(m,
     "\n protection: (%ld",
     zone->lowmem_reserve[0]);
for (i = 1; i < ARRAY_SIZE(zone->lowmem_reserve); i++)
  seq_printf(m, ", %ld", zone->lowmem_reserve[i]);
seq_putc(m, ')');

/* If unpopulated, no other information is useful */
if (!populated_zone(zone)) {
  seq_putc(m, '\n');
  return;
}

for (i = 0; i < NR_VM_ZONE_STAT_ITEMS; i++)
  seq_printf(m, "\n %-12s %lu", zone_stat_name(i),
      zone_page_state(zone, i));

#ifdef CONFIG_NUMA
fold_vm_zone_numa_events(zone);
for (i = 0; i < NR_VM_NUMA_EVENT_ITEMS; i++)
  seq_printf(m, "\n %-12s %lu", numa_stat_name(i),
      zone_numa_event_state(zone, i));
#endif

seq_printf(m, "\n pagesets");
for_each_online_cpu(i) {
  struct per_cpu_pages *pcp;
  struct per_cpu_zonestat __maybe_unused *pzstats;

  pcp = per_cpu_ptr(zone->per_cpu_pageset, i);
  seq_printf(m,
      "\n cpu: %i"
      "\n count: %i"
      "\n high: %i"
      "\n batch: %i"
      "\n high_min: %i"
      "\n high_max: %i",
      i,
      pcp->count,
      pcp->high,
      pcp->batch,
      pcp->high_min,
      pcp->high_max);
#ifdef CONFIG_SMP
  pzstats = per_cpu_ptr(zone->per_cpu_zonestats, i);
  seq_printf(m, "\n vm stats threshold: %d",
    pzstats->stat_threshold);
#endif
}
seq_printf(m,
     "\n node_unreclaimable: %u"
     "\n start_pfn: %lu",
     pgdat->kswapd_failures >= MAX_RECLAIM_RETRIES,
     zone->zone_start_pfn);
seq_putc(m, '\n');
}

/*
* Output information about zones in @pgdat.  All zones are printed regardless
* of whether they are populated or not: lowmem_reserve_ratio operates on the
* set of all zones and userspace would not be aware of such zones if they are
* suppressed here (zoneinfo displays the effect of lowmem_reserve_ratio).
*/
static int zoneinfo_show(struct seq_file *m, void *arg)
{
pg_data_t *pgdat = (pg_data_t *)arg;
walk_zones_in_node(m, pgdat, false, false, zoneinfo_show_print);
return 0;
}

static const struct seq_operations zoneinfo_op = {
.start = frag_start, /* iterate over all zones. The same as in
       * fragmentation. */
.next = frag_next,
.stop = frag_stop,
.show = zoneinfo_show,
};

#define NR_VMSTAT_ITEMS (NR_VM_ZONE_STAT_ITEMS + \
    NR_VM_NUMA_EVENT_ITEMS + \
    NR_VM_NODE_STAT_ITEMS + \
    NR_VM_STAT_ITEMS + \
    (IS_ENABLED(CONFIG_VM_EVENT_COUNTERS) ? \
     NR_VM_EVENT_ITEMS : 0))

static void *vmstat_start(struct seq_file *m, loff_t *pos)
{
unsigned long *v;
int i;

if (*pos >= NR_VMSTAT_ITEMS)
  return NULL;

BUILD_BUG_ON(ARRAY_SIZE(vmstat_text) != NR_VMSTAT_ITEMS);
fold_vm_numa_events();
v = kmalloc_array(NR_VMSTAT_ITEMS, sizeof(unsigned long), GFP_KERNEL);
m->private = v;
if (!v)
  return ERR_PTR(-ENOMEM);
for (i = 0; i < NR_VM_ZONE_STAT_ITEMS; i++)
  v[i] = global_zone_page_state(i);
v += NR_VM_ZONE_STAT_ITEMS;

#ifdef CONFIG_NUMA
for (i = 0; i < NR_VM_NUMA_EVENT_ITEMS; i++)
  v[i] = global_numa_event_state(i);
v += NR_VM_NUMA_EVENT_ITEMS;
#endif

for (i = 0; i < NR_VM_NODE_STAT_ITEMS; i++) {
  v[i] = global_node_page_state_pages(i);
  if (vmstat_item_print_in_thp(i))
   v[i] /= HPAGE_PMD_NR;
}
v += NR_VM_NODE_STAT_ITEMS;

global_dirty_limits(v + NR_DIRTY_BG_THRESHOLD,
       v + NR_DIRTY_THRESHOLD);
v[NR_MEMMAP_PAGES] = atomic_long_read(&nr_memmap_pages);
v[NR_MEMMAP_BOOT_PAGES] = atomic_long_read(&nr_memmap_boot_pages);
v += NR_VM_STAT_ITEMS;

#ifdef CONFIG_VM_EVENT_COUNTERS
all_vm_events(v);
v[PGPGIN] /= 2;  /* sectors -> kbytes */
v[PGPGOUT] /= 2;
#endif
return (unsigned long *)m->private + *pos;
}

static void *vmstat_next(struct seq_file *m, void *arg, loff_t *pos)
{
(*pos)++;
if (*pos >= NR_VMSTAT_ITEMS)
  return NULL;
return (unsigned long *)m->private + *pos;
}

static int vmstat_show(struct seq_file *m, void *arg)
{
unsigned long *l = arg;
unsigned long off = l - (unsigned long *)m->private;

seq_puts(m, vmstat_text[off]);
seq_put_decimal_ull(m, " ", *l);
seq_putc(m, '\n');

if (off == NR_VMSTAT_ITEMS - 1) {
  /*
* We've come to the end - add any deprecated counters to avoid
* breaking userspace which might depend on them being present.
*/
  seq_puts(m, "nr_unstable 0\n");
}
return 0;
}

static void vmstat_stop(struct seq_file *m, void *arg)
{
kfree(m->private);
m->private = NULL;
}

static const struct seq_operations vmstat_op = {
.start = vmstat_start,
.next = vmstat_next,
.stop = vmstat_stop,
.show = vmstat_show,
};
#endif /* CONFIG_PROC_FS */

#ifdef CONFIG_SMP
static DEFINE_PER_CPU(struct delayed_work, vmstat_work);
static int sysctl_stat_interval __read_mostly = HZ;
static int vmstat_late_init_done;

#ifdef CONFIG_PROC_FS
static void refresh_vm_stats(struct work_struct *work)
{
refresh_cpu_vm_stats(true);
}

static int vmstat_refresh(const struct ctl_table *table, int write,
     void *buffer, size_t *lenp, loff_t *ppos)
{
long val;
int err;
int i;

/*
* The regular update, every sysctl_stat_interval, may come later
* than expected: leaving a significant amount in per_cpu buckets.
* This is particularly misleading when checking a quantity of HUGE
* pages, immediately after running a test.  /proc/sys/vm/stat_refresh,
* which can equally be echo'ed to or cat'ted from (by root),
* can be used to update the stats just before reading them.
*
* Oh, and since global_zone_page_state() etc. are so careful to hide
* transiently negative values, report an error here if any of
* the stats is negative, so we know to go looking for imbalance.
*/
err = schedule_on_each_cpu(refresh_vm_stats);
if (err)
  return err;
for (i = 0; i < NR_VM_ZONE_STAT_ITEMS; i++) {
  /*
* Skip checking stats known to go negative occasionally.
*/
  switch (i) {
  case NR_ZONE_WRITE_PENDING:
  case NR_FREE_CMA_PAGES:
   continue;
  }
  val = atomic_long_read(&vm_zone_stat[i]);
  if (val < 0) {
   pr_warn("%s: %s %ld\n",
    __func__, zone_stat_name(i), val);
  }
}
for (i = 0; i < NR_VM_NODE_STAT_ITEMS; i++) {
  /*
* Skip checking stats known to go negative occasionally.
*/
  switch (i) {
  case NR_WRITEBACK:
   continue;
  }
  val = atomic_long_read(&vm_node_stat[i]);
  if (val < 0) {
   pr_warn("%s: %s %ld\n",
    __func__, node_stat_name(i), val);
  }
}
if (write)
  *ppos += *lenp;
else
  *lenp = 0;
return 0;
}
#endif /* CONFIG_PROC_FS */

static void vmstat_update(struct work_struct *w)
{
if (refresh_cpu_vm_stats(true)) {
  /*
* Counters were updated so we expect more updates
* to occur in the future. Keep on running the
* update worker thread.
*/
  queue_delayed_work_on(smp_processor_id(), mm_percpu_wq,
    this_cpu_ptr(&vmstat_work),
    round_jiffies_relative(sysctl_stat_interval));
}
}

/*
* Check if the diffs for a certain cpu indicate that
* an update is needed.
*/
static bool need_update(int cpu)
{
pg_data_t *last_pgdat = NULL;
struct zone *zone;

for_each_populated_zone(zone) {
  struct per_cpu_zonestat *pzstats = per_cpu_ptr(zone->per_cpu_zonestats, cpu);
  struct per_cpu_nodestat *n;

  /*
* The fast way of checking if there are any vmstat diffs.
*/
  if (memchr_inv(pzstats->vm_stat_diff, 0, sizeof(pzstats->vm_stat_diff)))
   return true;

  if (last_pgdat == zone->zone_pgdat)
   continue;
  last_pgdat = zone->zone_pgdat;
  n = per_cpu_ptr(zone->zone_pgdat->per_cpu_nodestats, cpu);
  if (memchr_inv(n->vm_node_stat_diff, 0, sizeof(n->vm_node_stat_diff)))
   return true;
}
return false;
}

/*
* Switch off vmstat processing and then fold all the remaining differentials
* until the diffs stay at zero. The function is used by NOHZ and can only be
* invoked when tick processing is not active.
*/
void quiet_vmstat(void)
{
if (system_state != SYSTEM_RUNNING)
  return;

if (!delayed_work_pending(this_cpu_ptr(&vmstat_work)))
  return;

if (!need_update(smp_processor_id()))
  return;

/*
* Just refresh counters and do not care about the pending delayed
* vmstat_update. It doesn't fire that often to matter and canceling
* it would be too expensive from this path.
* vmstat_shepherd will take care about that for us.
*/
refresh_cpu_vm_stats(false);
}

/*
* Shepherd worker thread that checks the
* differentials of processors that have their worker
* threads for vm statistics updates disabled because of
* inactivity.
*/
static void vmstat_shepherd(struct work_struct *w);

static DECLARE_DEFERRABLE_WORK(shepherd, vmstat_shepherd);

static void vmstat_shepherd(struct work_struct *w)
{
int cpu;

cpus_read_lock();
/* Check processors whose vmstat worker threads have been disabled */
for_each_online_cpu(cpu) {
  struct delayed_work *dw = &per_cpu(vmstat_work, cpu);

  /*
* In kernel users of vmstat counters either require the precise value and
* they are using zone_page_state_snapshot interface or they can live with
* an imprecision as the regular flushing can happen at arbitrary time and
* cumulative error can grow (see calculate_normal_threshold).
*
* From that POV the regular flushing can be postponed for CPUs that have
* been isolated from the kernel interference without critical
* infrastructure ever noticing. Skip regular flushing from vmstat_shepherd
* for all isolated CPUs to avoid interference with the isolated workload.
*/
  if (cpu_is_isolated(cpu))
   continue;

  if (!delayed_work_pending(dw) && need_update(cpu))
   queue_delayed_work_on(cpu, mm_percpu_wq, dw, 0);

  cond_resched();
}
cpus_read_unlock();

schedule_delayed_work(&shepherd,
  round_jiffies_relative(sysctl_stat_interval));
}

static void __init start_shepherd_timer(void)
{
int cpu;

for_each_possible_cpu(cpu) {
  INIT_DEFERRABLE_WORK(per_cpu_ptr(&vmstat_work, cpu),
   vmstat_update);

  /*
* For secondary CPUs during CPU hotplug scenarios,
* vmstat_cpu_online() will enable the work.
* mm/vmstat:online enables and disables vmstat_work
* symmetrically during CPU hotplug events.
*/
  if (!cpu_online(cpu))
   disable_delayed_work_sync(&per_cpu(vmstat_work, cpu));
}

schedule_delayed_work(&shepherd,
  round_jiffies_relative(sysctl_stat_interval));
}

static void __init init_cpu_node_state(void)
{
int node;

for_each_online_node(node) {
  if (!cpumask_empty(cpumask_of_node(node)))
   node_set_state(node, N_CPU);
}
}

static int vmstat_cpu_online(unsigned int cpu)
{
if (vmstat_late_init_done)
  refresh_zone_stat_thresholds();

if (!node_state(cpu_to_node(cpu), N_CPU)) {
  node_set_state(cpu_to_node(cpu), N_CPU);
}
enable_delayed_work(&per_cpu(vmstat_work, cpu));

return 0;
}

static int vmstat_cpu_down_prep(unsigned int cpu)
{
disable_delayed_work_sync(&per_cpu(vmstat_work, cpu));
return 0;
}

static int vmstat_cpu_dead(unsigned int cpu)
{
const struct cpumask *node_cpus;
int node;

node = cpu_to_node(cpu);

refresh_zone_stat_thresholds();
node_cpus = cpumask_of_node(node);
if (!cpumask_empty(node_cpus))
  return 0;

node_clear_state(node, N_CPU);

return 0;
}

static int __init vmstat_late_init(void)
{
refresh_zone_stat_thresholds();
vmstat_late_init_done = 1;

return 0;
}
late_initcall(vmstat_late_init);
#endif

#ifdef CONFIG_PROC_FS
static const struct ctl_table vmstat_table[] = {
#ifdef CONFIG_SMP
{
  .procname = "stat_interval",
  .data  = &sysctl_stat_interval,
  .maxlen  = sizeof(sysctl_stat_interval),
  .mode  = 0644,
  .proc_handler = proc_dointvec_jiffies,
},
{
  .procname = "stat_refresh",
  .data  = NULL,
  .maxlen  = 0,
  .mode  = 0600,
  .proc_handler = vmstat_refresh,
},
#endif
#ifdef CONFIG_NUMA
{
  .procname = "numa_stat",
  .data  = &sysctl_vm_numa_stat,
  .maxlen  = sizeof(int),
  .mode  = 0644,
  .proc_handler = sysctl_vm_numa_stat_handler,
  .extra1  = SYSCTL_ZERO,
  .extra2  = SYSCTL_ONE,
},
#endif
};
#endif

struct workqueue_struct *mm_percpu_wq;

void __init init_mm_internals(void)
{
int ret __maybe_unused;

mm_percpu_wq = alloc_workqueue("mm_percpu_wq", WQ_MEM_RECLAIM, 0);

#ifdef CONFIG_SMP
ret = cpuhp_setup_state_nocalls(CPUHP_MM_VMSTAT_DEAD, "mm/vmstat:dead",
     NULL, vmstat_cpu_dead);
if (ret < 0)
  pr_err("vmstat: failed to register 'dead' hotplug state\n");

ret = cpuhp_setup_state_nocalls(CPUHP_AP_ONLINE_DYN, "mm/vmstat:online",
     vmstat_cpu_online,
     vmstat_cpu_down_prep);
if (ret < 0)
  pr_err("vmstat: failed to register 'online' hotplug state\n");

cpus_read_lock();
init_cpu_node_state();
cpus_read_unlock();

start_shepherd_timer();
#endif
#ifdef CONFIG_PROC_FS
proc_create_seq("buddyinfo", 0444, NULL, &fragmentation_op);
proc_create_seq("pagetypeinfo", 0400, NULL, &pagetypeinfo_op);
proc_create_seq("vmstat", 0444, NULL, &vmstat_op);
proc_create_seq("zoneinfo", 0444, NULL, &zoneinfo_op);
register_sysctl_init("vm", vmstat_table);
#endif
}

#if defined(CONFIG_DEBUG_FS) && defined(CONFIG_COMPACTION)

/*
* Return an index indicating how much of the available free memory is
* unusable for an allocation of the requested size.
*/
static int unusable_free_index(unsigned int order,
    struct contig_page_info *info)
{
/* No free memory is interpreted as all free memory is unusable */
if (info->free_pages == 0)
  return 1000;

/*
* Index should be a value between 0 and 1. Return a value to 3
* decimal places.
*
* 0 => no fragmentation
* 1 => high fragmentation
*/
return div_u64((info->free_pages - (info->free_blocks_suitable << order)) * 1000ULL, info->free_pages);

}

static void unusable_show_print(struct seq_file *m,
     pg_data_t *pgdat, struct zone *zone)
{
unsigned int order;
int index;
struct contig_page_info info;

seq_printf(m, "Node %d, zone %8s ",
    pgdat->node_id,
    zone->name);
for (order = 0; order < NR_PAGE_ORDERS; ++order) {
  fill_contig_page_info(zone, order, &info);
  index = unusable_free_index(order, &info);
  seq_printf(m, "%d.%03d ", index / 1000, index % 1000);
}

seq_putc(m, '\n');
}

/*
* Display unusable free space index
*
* The unusable free space index measures how much of the available free
* memory cannot be used to satisfy an allocation of a given size and is a
* value between 0 and 1. The higher the value, the more of free memory is
* unusable and by implication, the worse the external fragmentation is. This
* can be expressed as a percentage by multiplying by 100.
*/
static int unusable_show(struct seq_file *m, void *arg)
{
pg_data_t *pgdat = (pg_data_t *)arg;

/* check memoryless node */
if (!node_state(pgdat->node_id, N_MEMORY))
  return 0;

walk_zones_in_node(m, pgdat, true, false, unusable_show_print);

return 0;
}

static const struct seq_operations unusable_sops = {
.start = frag_start,
.next = frag_next,
.stop = frag_stop,
.show = unusable_show,
};

DEFINE_SEQ_ATTRIBUTE(unusable);

static void extfrag_show_print(struct seq_file *m,
     pg_data_t *pgdat, struct zone *zone)
{
unsigned int order;
int index;

/* Alloc on stack as interrupts are disabled for zone walk */
struct contig_page_info info;

seq_printf(m, "Node %d, zone %8s ",
    pgdat->node_id,
    zone->name);
for (order = 0; order < NR_PAGE_ORDERS; ++order) {
  fill_contig_page_info(zone, order, &info);
  index = __fragmentation_index(order, &info);
  seq_printf(m, "%2d.%03d ", index / 1000, index % 1000);
}

seq_putc(m, '\n');
}

/*
* Display fragmentation index for orders that allocations would fail for
*/
static int extfrag_show(struct seq_file *m, void *arg)
{
pg_data_t *pgdat = (pg_data_t *)arg;

walk_zones_in_node(m, pgdat, true, false, extfrag_show_print);

return 0;
}

static const struct seq_operations extfrag_sops = {
.start = frag_start,
.next = frag_next,
.stop = frag_stop,
.show = extfrag_show,
};

DEFINE_SEQ_ATTRIBUTE(extfrag);

static int __init extfrag_debug_init(void)
{
struct dentry *extfrag_debug_root;

extfrag_debug_root = debugfs_create_dir("extfrag", NULL);

debugfs_create_file("unusable_index", 0444, extfrag_debug_root, NULL,
       &unusable_fops);

debugfs_create_file("extfrag_index", 0444, extfrag_debug_root, NULL,
       &extfrag_fops);

return 0;
}

--> --------------------

--> maximum size reached

--> --------------------

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