/*
   *  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];
  	}
  }
  
  /*
   * 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();

  }

  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;
  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;
  }

  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;
  }

  
  /*

   * 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;

  	}

  }

  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;
  	}

  }

  /*

   * 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);

  }
  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);
  }
  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);

  	}
  }

  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);
  	}
  }

  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_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);

  	}
  }

  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);
  	}
  }

  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_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);
  }
  
  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 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);
  }
  
  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_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;

  }

  /*

   * 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[i] += v;

  			}
  	}

  	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[] exsist.
   */

  void drain_zonestat(struct zone *zone, struct per_cpu_pageset *pset)
  {
  	int i;
  
  	for (i = 0; i < NR_VM_ZONE_STAT_ITEMS; i++)
  		if (pset->vm_stat_diff[i]) {
  			int v = pset->vm_stat_diff[i];
  			pset->vm_stat_diff[i] = 0;
  			atomic_long_add(v, &zone->vm_stat[i]);

  			atomic_long_add(v, &vm_zone_stat[i]);

  		}
  }

  #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 stat item.
   */
  unsigned long node_page_state(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;
  }

  #endif

  #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 < MAX_ORDER; order++) {
  		unsigned long blocks;
  
  		/* Count number of free blocks */
  		blocks = 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 (!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);
  }

  
  /* 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)

  #ifdef CONFIG_ZONE_DMA
  #define TEXT_FOR_DMA(xx) xx "_dma",
  #else
  #define TEXT_FOR_DMA(xx)
  #endif
  
  #ifdef CONFIG_ZONE_DMA32
  #define TEXT_FOR_DMA32(xx) xx "_dma32",
  #else
  #define TEXT_FOR_DMA32(xx)
  #endif
  
  #ifdef CONFIG_HIGHMEM
  #define TEXT_FOR_HIGHMEM(xx) xx "_high",
  #else
  #define TEXT_FOR_HIGHMEM(xx)
  #endif
  
  #define TEXTS_FOR_ZONES(xx) TEXT_FOR_DMA(xx) TEXT_FOR_DMA32(xx) xx "_normal", \
  					TEXT_FOR_HIGHMEM(xx) xx "_movable",
  
  const char * const vmstat_text[] = {

  	/* enum zone_stat_item countes */

  	"nr_free_pages",

  	"nr_zone_inactive_anon",
  	"nr_zone_active_anon",
  	"nr_zone_inactive_file",
  	"nr_zone_active_file",
  	"nr_zone_unevictable",

  	"nr_zone_write_pending",

  	"nr_mlock",

  	"nr_slab_reclaimable",
  	"nr_slab_unreclaimable",
  	"nr_page_table_pages",
  	"nr_kernel_stack",

  	"nr_bounce",

  #if IS_ENABLED(CONFIG_ZSMALLOC)
  	"nr_zspages",
  #endif

  #ifdef CONFIG_NUMA
  	"numa_hit",
  	"numa_miss",
  	"numa_foreign",
  	"numa_interleave",
  	"numa_local",
  	"numa_other",
  #endif

  	"nr_free_cma",

  	/* Node-based counters */
  	"nr_inactive_anon",
  	"nr_active_anon",
  	"nr_inactive_file",
  	"nr_active_file",
  	"nr_unevictable",
  	"nr_isolated_anon",
  	"nr_isolated_file",
  	"nr_pages_scanned",

  	"workingset_refault",
  	"workingset_activate",
  	"workingset_nodereclaim",

  	"nr_anon_pages",
  	"nr_mapped",

  	"nr_file_pages",
  	"nr_dirty",
  	"nr_writeback",
  	"nr_writeback_temp",
  	"nr_shmem",
  	"nr_shmem_hugepages",
  	"nr_shmem_pmdmapped",
  	"nr_anon_transparent_hugepages",
  	"nr_unstable",

  	"nr_vmscan_write",
  	"nr_vmscan_immediate_reclaim",
  	"nr_dirtied",
  	"nr_written",

  	/* enum writeback_stat_item counters */

  	"nr_dirty_threshold",
  	"nr_dirty_background_threshold",
  
  #ifdef CONFIG_VM_EVENT_COUNTERS

  	/* enum vm_event_item counters */

  	"pgpgin",
  	"pgpgout",
  	"pswpin",
  	"pswpout",
  
  	TEXTS_FOR_ZONES("pgalloc")

  	TEXTS_FOR_ZONES("allocstall")
  	TEXTS_FOR_ZONES("pgskip")

  
  	"pgfree",
  	"pgactivate",
  	"pgdeactivate",
  
  	"pgfault",
  	"pgmajfault",

  	"pglazyfreed",

  	"pgrefill",
  	"pgsteal_kswapd",
  	"pgsteal_direct",
  	"pgscan_kswapd",
  	"pgscan_direct",

  	"pgscan_direct_throttle",

  
  #ifdef CONFIG_NUMA
  	"zone_reclaim_failed",
  #endif
  	"pginodesteal",
  	"slabs_scanned",

  	"kswapd_inodesteal",
  	"kswapd_low_wmark_hit_quickly",
  	"kswapd_high_wmark_hit_quickly",

  	"pageoutrun",

  
  	"pgrotated",

  	"drop_pagecache",
  	"drop_slab",

  #ifdef CONFIG_NUMA_BALANCING
  	"numa_pte_updates",

  	"numa_huge_pte_updates",

  	"numa_hint_faults",
  	"numa_hint_faults_local",
  	"numa_pages_migrated",
  #endif

  #ifdef CONFIG_MIGRATION
  	"pgmigrate_success",
  	"pgmigrate_fail",
  #endif

  #ifdef CONFIG_COMPACTION

  	"compact_migrate_scanned",
  	"compact_free_scanned",
  	"compact_isolated",

  	"compact_stall",
  	"compact_fail",
  	"compact_success",

  	"compact_daemon_wake",

  #endif
  
  #ifdef CONFIG_HUGETLB_PAGE
  	"htlb_buddy_alloc_success",
  	"htlb_buddy_alloc_fail",
  #endif
  	"unevictable_pgs_culled",
  	"unevictable_pgs_scanned",
  	"unevictable_pgs_rescued",
  	"unevictable_pgs_mlocked",
  	"unevictable_pgs_munlocked",
  	"unevictable_pgs_cleared",
  	"unevictable_pgs_stranded",

  
  #ifdef CONFIG_TRANSPARENT_HUGEPAGE
  	"thp_fault_alloc",
  	"thp_fault_fallback",
  	"thp_collapse_alloc",
  	"thp_collapse_alloc_failed",

  	"thp_file_alloc",
  	"thp_file_mapped",

  	"thp_split_page",
  	"thp_split_page_failed",

  	"thp_deferred_split_page",

  	"thp_split_pmd",

  	"thp_zero_page_alloc",
  	"thp_zero_page_alloc_failed",

  #endif

  #ifdef CONFIG_MEMORY_BALLOON
  	"balloon_inflate",
  	"balloon_deflate",
  #ifdef CONFIG_BALLOON_COMPACTION
  	"balloon_migrate",
  #endif
  #endif /* CONFIG_MEMORY_BALLOON */

  #ifdef CONFIG_DEBUG_TLBFLUSH

  #ifdef CONFIG_SMP

  	"nr_tlb_remote_flush",
  	"nr_tlb_remote_flush_received",

  #endif /* CONFIG_SMP */

  	"nr_tlb_local_flush_all",
  	"nr_tlb_local_flush_one",

  #endif /* CONFIG_DEBUG_TLBFLUSH */

  #ifdef CONFIG_DEBUG_VM_VMACACHE
  	"vmacache_find_calls",
  	"vmacache_find_hits",

  	"vmacache_full_flushes",

  #endif

  #endif /* CONFIG_VM_EVENTS_COUNTERS */
  };

  #endif /* CONFIG_PROC_FS || CONFIG_SYSFS || CONFIG_NUMA */

  #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 all the zones in a node and print using a callback */
  static void walk_zones_in_node(struct seq_file *m, pg_data_t *pgdat,
  		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 (!populated_zone(zone))
  			continue;
  
  		spin_lock_irqsave(&zone->lock, flags);
  		print(m, pgdat, zone);
  		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 < MAX_ORDER; ++order)
  		seq_printf(m, "%6lu ", zone->free_area[order].nr_free);
  	seq_putc(m, '
  ');
  }
  
  /*
   * 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, 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 < MAX_ORDER; ++order) {
  			unsigned long freecount = 0;
  			struct free_area *area;
  			struct list_head *curr;
  
  			area = &(zone->free_area[order]);
  
  			list_for_each(curr, &area->free_list[mtype])
  				freecount++;
  			seq_printf(m, "%6lu ", freecount);
  		}

  		seq_putc(m, '
  ');
  	}

  }
  
  /* Print out the free pages at each order for each migatetype */
  static int 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 < MAX_ORDER; ++order)
  		seq_printf(m, "%6d ", order);
  	seq_putc(m, '
  ');
  
  	walk_zones_in_node(m, pgdat, pagetypeinfo_showfree_print);
  
  	return 0;
  }
  
  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;
  
  		if (!pfn_valid(pfn))
  			continue;
  
  		page = pfn_to_page(pfn);

  
  		/* Watch for unexpected holes punched in the memmap */
  		if (!memmap_valid_within(pfn, page, zone))

  			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, '
  ');
  }
  
  /* Print out the free pages at each order for each migratetype */
  static int pagetypeinfo_showblockcount(struct seq_file *m, void *arg)
  {
  	int mtype;
  	pg_data_t *pgdat = (pg_data_t *)arg;
  
  	seq_printf(m, "
  %-23s", "Number of blocks type ");
  	for (mtype = 0; mtype < MIGRATE_TYPES; mtype++)
  		seq_printf(m, "%12s ", migratetype_names[mtype]);
  	seq_putc(m, '
  ');
  	walk_zones_in_node(m, pgdat, pagetypeinfo_showblockcount_print);
  
  	return 0;
  }

  /*
   * 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, "
  %-23s", "Number of mixed blocks ");
  	for (mtype = 0; mtype < MIGRATE_TYPES; mtype++)
  		seq_printf(m, "%12s ", migratetype_names[mtype]);
  	seq_putc(m, '
  ');
  
  	walk_zones_in_node(m, pgdat, 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
  ", pageblock_order);
  	seq_printf(m, "Pages per block:  %lu
  ", pageblock_nr_pages);
  	seq_putc(m, '
  ');
  	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 int fragmentation_open(struct inode *inode, struct file *file)
  {
  	return seq_open(file, &fragmentation_op);
  }
  
  static const struct file_operations fragmentation_file_operations = {
  	.open		= fragmentation_open,
  	.read		= seq_read,
  	.llseek		= seq_lseek,
  	.release	= seq_release,
  };

  static const struct seq_operations pagetypeinfo_op = {

  	.start	= frag_start,
  	.next	= frag_next,
  	.stop	= frag_stop,
  	.show	= pagetypeinfo_show,
  };

  static int pagetypeinfo_open(struct inode *inode, struct file *file)
  {
  	return seq_open(file, &pagetypeinfo_op);
  }
  
  static const struct file_operations pagetypeinfo_file_ops = {
  	.open		= pagetypeinfo_open,
  	.read		= seq_read,
  	.llseek		= seq_lseek,
  	.release	= seq_release,
  };

  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;
  	}
  
  	/* The zone must be somewhere! */
  	WARN_ON_ONCE(1);
  	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, "
    per-node stats");
  		for (i = 0; i < NR_VM_NODE_STAT_ITEMS; i++) {
  			seq_printf(m, "
        %-12s %lu",
  				vmstat_text[i + NR_VM_ZONE_STAT_ITEMS],
  				node_page_state(pgdat, i));
  		}
  	}

  	seq_printf(m,
  		   "
    pages free     %lu"
  		   "
          min      %lu"
  		   "
          low      %lu"
  		   "
          high     %lu"

  		   "
     node_scanned  %lu"

  		   "
          spanned  %lu"

  		   "
          present  %lu"
  		   "
          managed  %lu",

  		   zone_page_state(zone, NR_FREE_PAGES),

  		   min_wmark_pages(zone),
  		   low_wmark_pages(zone),
  		   high_wmark_pages(zone),

  		   node_page_state(zone->zone_pgdat, NR_PAGES_SCANNED),

  		   zone->spanned_pages,

  		   zone->present_pages,
  		   zone->managed_pages);

  
  	for (i = 0; i < NR_VM_ZONE_STAT_ITEMS; i++)

  		seq_printf(m, "
        %-12s %lu", vmstat_text[i],

  				zone_page_state(zone, i));
  
  	seq_printf(m,

  		   "
          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_printf(m,
  		   ")"
  		   "
    pagesets");
  	for_each_online_cpu(i) {
  		struct per_cpu_pageset *pageset;

  		pageset = per_cpu_ptr(zone->pageset, i);

  		seq_printf(m,
  			   "
      cpu: %i"
  			   "
                count: %i"
  			   "
                high:  %i"
  			   "
                batch: %i",
  			   i,
  			   pageset->pcp.count,
  			   pageset->pcp.high,
  			   pageset->pcp.batch);

  #ifdef CONFIG_SMP

  		seq_printf(m, "
    vm stats threshold: %d",
  				pageset->stat_threshold);

  #endif

  	}

  	seq_printf(m,

  		   "
    node_unreclaimable:  %u"
  		   "
    start_pfn:           %lu"
  		   "
    node_inactive_ratio: %u",
  		   !pgdat_reclaimable(zone->zone_pgdat),

  		   zone->zone_start_pfn,

  		   zone->zone_pgdat->inactive_ratio);

  	seq_putc(m, '
  ');
  }
  
  /*
   * Output information about zones in @pgdat.
   */
  static int zoneinfo_show(struct seq_file *m, void *arg)
  {
  	pg_data_t *pgdat = (pg_data_t *)arg;
  	walk_zones_in_node(m, pgdat, 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,
  };

  static int zoneinfo_open(struct inode *inode, struct file *file)
  {
  	return seq_open(file, &zoneinfo_op);
  }
  
  static const struct file_operations proc_zoneinfo_file_operations = {
  	.open		= zoneinfo_open,
  	.read		= seq_read,
  	.llseek		= seq_lseek,
  	.release	= seq_release,
  };

  enum writeback_stat_item {
  	NR_DIRTY_THRESHOLD,
  	NR_DIRTY_BG_THRESHOLD,
  	NR_VM_WRITEBACK_STAT_ITEMS,
  };

  static void *vmstat_start(struct seq_file *m, loff_t *pos)
  {

  	unsigned long *v;

  	int i, stat_items_size;

  
  	if (*pos >= ARRAY_SIZE(vmstat_text))
  		return NULL;

  	stat_items_size = NR_VM_ZONE_STAT_ITEMS * sizeof(unsigned long) +

  			  NR_VM_NODE_STAT_ITEMS * sizeof(unsigned long) +

  			  NR_VM_WRITEBACK_STAT_ITEMS * sizeof(unsigned long);

  #ifdef CONFIG_VM_EVENT_COUNTERS

  	stat_items_size += sizeof(struct vm_event_state);

  #endif

  
  	v = kmalloc(stat_items_size, GFP_KERNEL);

  	m->private = v;
  	if (!v)

  		return ERR_PTR(-ENOMEM);

  	for (i = 0; i < NR_VM_ZONE_STAT_ITEMS; i++)
  		v[i] = global_page_state(i);

  	v += NR_VM_ZONE_STAT_ITEMS;

  	for (i = 0; i < NR_VM_NODE_STAT_ITEMS; i++)
  		v[i] = global_node_page_state(i);
  	v += NR_VM_NODE_STAT_ITEMS;

  	global_dirty_limits(v + NR_DIRTY_BG_THRESHOLD,
  			    v + NR_DIRTY_THRESHOLD);
  	v += NR_VM_WRITEBACK_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 >= ARRAY_SIZE(vmstat_text))
  		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, '
  ');

  	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,
  };

  static int vmstat_open(struct inode *inode, struct file *file)
  {
  	return seq_open(file, &vmstat_op);
  }
  
  static const struct file_operations proc_vmstat_file_operations = {
  	.open		= vmstat_open,
  	.read		= seq_read,
  	.llseek		= seq_lseek,
  	.release	= seq_release,
  };

  #endif /* CONFIG_PROC_FS */

  #ifdef CONFIG_SMP

  static struct workqueue_struct *vmstat_wq;

  static DEFINE_PER_CPU(struct delayed_work, vmstat_work);

  int sysctl_stat_interval __read_mostly = HZ;

  #ifdef CONFIG_PROC_FS
  static void refresh_vm_stats(struct work_struct *work)
  {
  	refresh_cpu_vm_stats(true);
  }
  
  int vmstat_refresh(struct ctl_table *table, int write,
  		   void __user *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_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++) {

  		val = atomic_long_read(&vm_zone_stat[i]);

  		if (val < 0) {
  			switch (i) {

  			case NR_PAGES_SCANNED:
  				/*

  				 * This is often seen to go negative in

  				 * recent kernels, but not to go permanently
  				 * negative.  Whilst it would be nicer not to
  				 * have exceptions, rooting them out would be
  				 * another task, of rather low priority.
  				 */
  				break;
  			default:
  				pr_warn("%s: %s %ld
  ",
  					__func__, vmstat_text[i], val);
  				err = -EINVAL;
  				break;
  			}
  		}
  	}
  	if (err)
  		return err;
  	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(), vmstat_wq,

  				this_cpu_ptr(&vmstat_work),
  				round_jiffies_relative(sysctl_stat_interval));

  	}
  }
  
  /*

   * 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.
   */

  /*

   * Check if the diffs for a certain cpu indicate that
   * an update is needed.
   */
  static bool need_update(int cpu)
  {
  	struct zone *zone;
  
  	for_each_populated_zone(zone) {
  		struct per_cpu_pageset *p = per_cpu_ptr(zone->pageset, cpu);
  
  		BUILD_BUG_ON(sizeof(p->vm_stat_diff[0]) != 1);
  		/*
  		 * The fast way of checking if there are any vmstat diffs.
  		 * This works because the diffs are byte sized items.
  		 */
  		if (memchr_inv(p->vm_stat_diff, 0, NR_VM_ZONE_STAT_ITEMS))
  			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;
  
  	get_online_cpus();
  	/* Check processors whose vmstat worker threads have been disabled */

  	for_each_online_cpu(cpu) {

  		struct delayed_work *dw = &per_cpu(vmstat_work, cpu);

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

  	}

  	put_online_cpus();
  
  	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);

  	vmstat_wq = alloc_workqueue("vmstat", WQ_FREEZABLE|WQ_MEM_RECLAIM, 0);

  	schedule_delayed_work(&shepherd,
  		round_jiffies_relative(sysctl_stat_interval));

  }

  static void __init init_cpu_node_state(void)
  {
  	int cpu;
  
  	get_online_cpus();
  	for_each_online_cpu(cpu)
  		node_set_state(cpu_to_node(cpu), N_CPU);
  	put_online_cpus();
  }

  static void vmstat_cpu_dead(int node)
  {
  	int cpu;
  
  	get_online_cpus();
  	for_each_online_cpu(cpu)
  		if (cpu_to_node(cpu) == node)
  			goto end;
  
  	node_clear_state(node, N_CPU);
  end:
  	put_online_cpus();
  }

  /*
   * Use the cpu notifier to insure that the thresholds are recalculated
   * when necessary.
   */

  static int vmstat_cpuup_callback(struct notifier_block *nfb,

  		unsigned long action,
  		void *hcpu)
  {

  	long cpu = (long)hcpu;

  	switch (action) {

  	case CPU_ONLINE:
  	case CPU_ONLINE_FROZEN:

  		refresh_zone_stat_thresholds();

  		node_set_state(cpu_to_node(cpu), N_CPU);

  		break;
  	case CPU_DOWN_PREPARE:
  	case CPU_DOWN_PREPARE_FROZEN:

  		cancel_delayed_work_sync(&per_cpu(vmstat_work, cpu));

  		break;
  	case CPU_DOWN_FAILED:
  	case CPU_DOWN_FAILED_FROZEN:

  		break;

  	case CPU_DEAD:

  	case CPU_DEAD_FROZEN:

  		refresh_zone_stat_thresholds();

  		vmstat_cpu_dead(cpu_to_node(cpu));

  		break;
  	default:
  		break;

  	}
  	return NOTIFY_OK;
  }

  static struct notifier_block vmstat_notifier =

  	{ &vmstat_cpuup_callback, NULL, 0 };

  #endif

  static int __init setup_vmstat(void)

  {

  #ifdef CONFIG_SMP

  	cpu_notifier_register_begin();
  	__register_cpu_notifier(&vmstat_notifier);

  	init_cpu_node_state();

  	start_shepherd_timer();

  	cpu_notifier_register_done();

  #endif
  #ifdef CONFIG_PROC_FS
  	proc_create("buddyinfo", S_IRUGO, NULL, &fragmentation_file_operations);

  	proc_create("pagetypeinfo", S_IRUGO, NULL, &pagetypeinfo_file_ops);

  	proc_create("vmstat", S_IRUGO, NULL, &proc_vmstat_file_operations);

  	proc_create("zoneinfo", S_IRUGO, NULL, &proc_zoneinfo_file_operations);

  #endif

  	return 0;
  }
  module_init(setup_vmstat)

  
  #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 < MAX_ORDER; ++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, '
  ');
  }
  
  /*
   * 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, unusable_show_print);
  
  	return 0;
  }
  
  static const struct seq_operations unusable_op = {
  	.start	= frag_start,
  	.next	= frag_next,
  	.stop	= frag_stop,
  	.show	= unusable_show,
  };
  
  static int unusable_open(struct inode *inode, struct file *file)
  {
  	return seq_open(file, &unusable_op);
  }
  
  static const struct file_operations unusable_file_ops = {
  	.open		= unusable_open,
  	.read		= seq_read,
  	.llseek		= seq_lseek,
  	.release	= seq_release,
  };

  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 < MAX_ORDER; ++order) {
  		fill_contig_page_info(zone, order, &info);

  		index = __fragmentation_index(order, &info);

  		seq_printf(m, "%d.%03d ", index / 1000, index % 1000);
  	}
  
  	seq_putc(m, '
  ');
  }
  
  /*
   * 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, extfrag_show_print);
  
  	return 0;
  }
  
  static const struct seq_operations extfrag_op = {
  	.start	= frag_start,
  	.next	= frag_next,
  	.stop	= frag_stop,
  	.show	= extfrag_show,
  };
  
  static int extfrag_open(struct inode *inode, struct file *file)
  {
  	return seq_open(file, &extfrag_op);
  }
  
  static const struct file_operations extfrag_file_ops = {
  	.open		= extfrag_open,
  	.read		= seq_read,
  	.llseek		= seq_lseek,
  	.release	= seq_release,
  };

  static int __init extfrag_debug_init(void)
  {

  	struct dentry *extfrag_debug_root;

  	extfrag_debug_root = debugfs_create_dir("extfrag", NULL);
  	if (!extfrag_debug_root)
  		return -ENOMEM;
  
  	if (!debugfs_create_file("unusable_index", 0444,
  			extfrag_debug_root, NULL, &unusable_file_ops))

  		goto fail;

  	if (!debugfs_create_file("extfrag_index", 0444,
  			extfrag_debug_root, NULL, &extfrag_file_ops))

  		goto fail;

  	return 0;

  fail:
  	debugfs_remove_recursive(extfrag_debug_root);
  	return -ENOMEM;

  }
  
  module_init(extfrag_debug_init);
  #endif