/*
   *  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>

   */

  #include <linux/mm.h>

  #include <linux/err.h>

  #include <linux/module.h>

  #include <linux/cpu.h>

  #include <linux/sched.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, cpumask_t *cpumask)
  {

  	int cpu;

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

  	for_each_cpu_mask(cpu, *cpumask) {

  		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, &cpu_online_map);

  	put_online_cpus();

  }

  EXPORT_SYMBOL_GPL(all_vm_events);

  
  #ifdef CONFIG_HOTPLUG
  /*
   * 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_HOTPLUG */
  
  #endif /* CONFIG_VM_EVENT_COUNTERS */

  /*
   * Manage combined zone based / global counters
   *
   * vm_stat contains the global counters
   */
  atomic_long_t vm_stat[NR_VM_ZONE_STAT_ITEMS];
  EXPORT_SYMBOL(vm_stat);
  
  #ifdef CONFIG_SMP

  static int calculate_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->present_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.

   */

  static void refresh_zone_stat_thresholds(void)

  {

  	struct zone *zone;
  	int cpu;
  	int threshold;
  
  	for_each_zone(zone) {
  
  		if (!zone->present_pages)
  			continue;
  
  		threshold = calculate_threshold(zone);
  
  		for_each_online_cpu(cpu)
  			zone_pcp(zone, cpu)->stat_threshold = threshold;
  	}

  }
  
  /*
   * For use when we know that interrupts are disabled.
   */
  void __mod_zone_page_state(struct zone *zone, enum zone_stat_item item,
  				int delta)
  {

  	struct per_cpu_pageset *pcp = zone_pcp(zone, smp_processor_id());
  	s8 *p = pcp->vm_stat_diff + item;

  	long x;

  	x = delta + *p;

  	if (unlikely(x > pcp->stat_threshold || x < -pcp->stat_threshold)) {

  		zone_page_state_add(x, zone, item);
  		x = 0;
  	}

  	*p = x;
  }
  EXPORT_SYMBOL(__mod_zone_page_state);
  
  /*
   * For an unknown interrupt state
   */
  void mod_zone_page_state(struct zone *zone, enum zone_stat_item item,
  					int 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);
  
  /*
   * 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 *pcp = zone_pcp(zone, smp_processor_id());
  	s8 *p = pcp->vm_stat_diff + item;

  
  	(*p)++;

  	if (unlikely(*p > pcp->stat_threshold)) {
  		int overstep = pcp->stat_threshold / 2;
  
  		zone_page_state_add(*p + overstep, zone, item);
  		*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 __dec_zone_state(struct zone *zone, enum zone_stat_item item)

  {

  	struct per_cpu_pageset *pcp = zone_pcp(zone, smp_processor_id());
  	s8 *p = pcp->vm_stat_diff + item;

  
  	(*p)--;

  	if (unlikely(*p < - pcp->stat_threshold)) {
  		int overstep = pcp->stat_threshold / 2;
  
  		zone_page_state_add(*p - overstep, zone, item);
  		*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 inc_zone_state(struct zone *zone, enum zone_stat_item item)
  {
  	unsigned long flags;
  
  	local_irq_save(flags);
  	__inc_zone_state(zone, item);
  	local_irq_restore(flags);
  }

  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);
  
  /*
   * Update the zone counters for one cpu.

   *

   * The cpu specified must be either the current cpu or a processor that
   * is not online. If it is the current cpu then the execution thread must
   * be pinned to 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.

   */
  void refresh_cpu_vm_stats(int cpu)
  {
  	struct zone *zone;
  	int i;

  	int global_diff[NR_VM_ZONE_STAT_ITEMS] = { 0, };

  
  	for_each_zone(zone) {

  		struct per_cpu_pageset *p;

  		if (!populated_zone(zone))
  			continue;

  		p = zone_pcp(zone, cpu);

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

  			if (p->vm_stat_diff[i]) {

  				unsigned long flags;
  				int v;

  				local_irq_save(flags);

  				v = p->vm_stat_diff[i];

  				p->vm_stat_diff[i] = 0;

  				local_irq_restore(flags);
  				atomic_long_add(v, &zone->vm_stat[i]);
  				global_diff[i] += v;

  #ifdef CONFIG_NUMA
  				/* 3 seconds idle till flush */
  				p->expire = 3;
  #endif

  			}

  		cond_resched();

  #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 (!p->expire || !p->pcp.count)

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

  		if (p->pcp.count)
  			drain_zone_pages(zone, &p->pcp);

  #endif

  	}

  
  	for (i = 0; i < NR_VM_ZONE_STAT_ITEMS; i++)
  		if (global_diff[i])
  			atomic_long_add(global_diff[i], &vm_stat[i]);

  }

  #endif

  #ifdef CONFIG_NUMA
  /*
   * zonelist = the list of zones passed to the allocator
   * z 	    = the zone from which the allocation occurred.
   *
   * Must be called with interrupts disabled.
   */

  void zone_statistics(struct zone *preferred_zone, struct zone *z)

  {

  	if (z->zone_pgdat == preferred_zone->zone_pgdat) {

  		__inc_zone_state(z, NUMA_HIT);
  	} else {
  		__inc_zone_state(z, NUMA_MISS);

  		__inc_zone_state(preferred_zone, NUMA_FOREIGN);

  	}

  	if (z->node == numa_node_id())

  		__inc_zone_state(z, NUMA_LOCAL);
  	else
  		__inc_zone_state(z, NUMA_OTHER);
  }
  #endif

  #ifdef CONFIG_PROC_FS
  
  #include <linux/seq_file.h>

  static char * const migratetype_names[MIGRATE_TYPES] = {
  	"Unmovable",
  	"Reclaimable",
  	"Movable",
  	"Reserve",

  	"Isolate",

  };

  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);

  	}
  }
  
  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 = start_pfn + zone->spanned_pages;
  	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);
  		mtype = get_pageblock_migratetype(page);
  
  		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;
  }
  
  /*
   * 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_HIGH_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);

  	return 0;
  }

  const struct seq_operations fragmentation_op = {

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

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

  #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",

  static const char * const vmstat_text[] = {

  	/* Zoned VM counters */

  	"nr_free_pages",

  	"nr_inactive",

  	"nr_active",

  	"nr_anon_pages",

  	"nr_mapped",

  	"nr_file_pages",

  	"nr_dirty",
  	"nr_writeback",

  	"nr_slab_reclaimable",
  	"nr_slab_unreclaimable",

  	"nr_page_table_pages",

  	"nr_unstable",

  	"nr_bounce",

  	"nr_vmscan_write",

  	"nr_writeback_temp",

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

  #ifdef CONFIG_VM_EVENT_COUNTERS

  	"pgpgin",
  	"pgpgout",
  	"pswpin",
  	"pswpout",

  	TEXTS_FOR_ZONES("pgalloc")

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

  	TEXTS_FOR_ZONES("pgrefill")
  	TEXTS_FOR_ZONES("pgsteal")
  	TEXTS_FOR_ZONES("pgscan_kswapd")
  	TEXTS_FOR_ZONES("pgscan_direct")

  
  	"pginodesteal",
  	"slabs_scanned",
  	"kswapd_steal",
  	"kswapd_inodesteal",
  	"pageoutrun",
  	"allocstall",
  
  	"pgrotated",

  #ifdef CONFIG_HUGETLB_PAGE
  	"htlb_buddy_alloc_success",
  	"htlb_buddy_alloc_fail",
  #endif

  #endif

  };

  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);
  	seq_printf(m,
  		   "
    pages free     %lu"
  		   "
          min      %lu"
  		   "
          low      %lu"
  		   "
          high     %lu"
  		   "
          scanned  %lu (a: %lu i: %lu)"
  		   "
          spanned  %lu"
  		   "
          present  %lu",
  		   zone_page_state(zone, NR_FREE_PAGES),
  		   zone->pages_min,
  		   zone->pages_low,
  		   zone->pages_high,
  		   zone->pages_scanned,
  		   zone->nr_scan_active, zone->nr_scan_inactive,
  		   zone->spanned_pages,
  		   zone->present_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: (%lu",
  		   zone->lowmem_reserve[0]);
  	for (i = 1; i < ARRAY_SIZE(zone->lowmem_reserve); i++)
  		seq_printf(m, ", %lu", zone->lowmem_reserve[i]);
  	seq_printf(m,
  		   ")"
  		   "
    pagesets");
  	for_each_online_cpu(i) {
  		struct per_cpu_pageset *pageset;

  
  		pageset = zone_pcp(zone, 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,
  		   "
    all_unreclaimable: %u"
  		   "
    prev_priority:     %i"
  		   "
    start_pfn:         %lu",

  			   zone_is_all_unreclaimable(zone),

  		   zone->prev_priority,
  		   zone->zone_start_pfn);
  	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;
  }

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

  	unsigned long *v;

  #ifdef CONFIG_VM_EVENT_COUNTERS
  	unsigned long *e;
  #endif

  	int i;

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

  #ifdef CONFIG_VM_EVENT_COUNTERS

  	v = kmalloc(NR_VM_ZONE_STAT_ITEMS * sizeof(unsigned long)

  			+ sizeof(struct vm_event_state), GFP_KERNEL);
  #else
  	v = kmalloc(NR_VM_ZONE_STAT_ITEMS * sizeof(unsigned long),
  			GFP_KERNEL);
  #endif

  	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);

  #ifdef CONFIG_VM_EVENT_COUNTERS
  	e = v + NR_VM_ZONE_STAT_ITEMS;
  	all_vm_events(e);
  	e[PGPGIN] /= 2;		/* sectors -> kbytes */
  	e[PGPGOUT] /= 2;
  #endif

  	return v + *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_printf(m, "%s %lu
  ", vmstat_text[off], *l);
  	return 0;
  }
  
  static void vmstat_stop(struct seq_file *m, void *arg)
  {
  	kfree(m->private);
  	m->private = NULL;
  }

  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);

  int sysctl_stat_interval __read_mostly = HZ;

  
  static void vmstat_update(struct work_struct *w)
  {
  	refresh_cpu_vm_stats(smp_processor_id());

  	schedule_delayed_work(&__get_cpu_var(vmstat_work),
  		sysctl_stat_interval);

  }

  static void __cpuinit start_cpu_timer(int cpu)

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

  	INIT_DELAYED_WORK_DEFERRABLE(vmstat_work, vmstat_update);

  	schedule_delayed_work_on(cpu, vmstat_work, HZ + cpu);
  }

  /*
   * Use the cpu notifier to insure that the thresholds are recalculated
   * when necessary.
   */
  static int __cpuinit 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:
  		start_cpu_timer(cpu);
  		break;
  	case CPU_DOWN_PREPARE:
  	case CPU_DOWN_PREPARE_FROZEN:
  		cancel_rearming_delayed_work(&per_cpu(vmstat_work, cpu));
  		per_cpu(vmstat_work, cpu).work.func = NULL;
  		break;
  	case CPU_DOWN_FAILED:
  	case CPU_DOWN_FAILED_FROZEN:
  		start_cpu_timer(cpu);
  		break;

  	case CPU_DEAD:

  	case CPU_DEAD_FROZEN:

  		refresh_zone_stat_thresholds();
  		break;
  	default:
  		break;

  	}
  	return NOTIFY_OK;
  }
  
  static struct notifier_block __cpuinitdata vmstat_notifier =
  	{ &vmstat_cpuup_callback, NULL, 0 };

  static int __init setup_vmstat(void)

  {

  	int cpu;

  	refresh_zone_stat_thresholds();
  	register_cpu_notifier(&vmstat_notifier);

  
  	for_each_online_cpu(cpu)
  		start_cpu_timer(cpu);

  	return 0;
  }
  module_init(setup_vmstat)
  #endif