FreeBSD/Linux Kernel Cross Reference
sys/mm/vmstat.c

     /*
      *  linux/mm/vmstat.c
      *
      *  Manages VM statistics
      *  Copyright (C) 1991, 1992, 1993, 1994  Linus Torvalds
      *
      *  zoned VM statistics
      *  Copyright (C) 2006 Silicon Graphics, Inc.,
      *              Christoph Lameter <christoph@lameter.com>
     */
    #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/vmstat.h>
    #include <linux/sched.h>
    #include <linux/math64.h>
    #include <linux/writeback.h>
    #include <linux/compaction.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);
    
    #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] __cacheline_aligned_in_smp;
    EXPORT_SYMBOL(vm_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->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.
    */
   void refresh_zone_stat_thresholds(void)
   {
           struct zone *zone;
           int cpu;
           int threshold;
   
           for_each_populated_zone(zone) {
                   unsigned long max_drift, tolerate_drift;
   
                   threshold = calculate_normal_threshold(zone);
   
                   for_each_online_cpu(cpu)
                           per_cpu_ptr(zone->pageset, cpu)->stat_threshold
                                                           = 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_possible_cpu(cpu)
                           per_cpu_ptr(zone->pageset, 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 __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);
   
   /*
    * 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_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 __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_zone_page_state(struct page *page, enum zone_stat_item item)
   {
           __dec_zone_state(page_zone(page), item);
   }
   EXPORT_SYMBOL(__dec_zone_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_state(struct zone *zone,
          enum zone_stat_item item, int 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,
                                           int delta)
   {
           mod_state(zone, item, delta, 0);
   }
   EXPORT_SYMBOL(mod_zone_page_state);
   
   void inc_zone_state(struct zone *zone, enum zone_stat_item item)
   {
           mod_state(zone, item, 1, 1);
   }
   
   void inc_zone_page_state(struct page *page, enum zone_stat_item item)
   {
           mod_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_state(page_zone(page), item, -1, -1);
   }
   EXPORT_SYMBOL(dec_zone_page_state);
   #else
   /*
    * Use interrupt disable to serialize counter updates
    */
   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);
   
   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);
   #endif
   
   /*
    * 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_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]) {
                                   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]);
   }
   
   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_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.
    *
    * When __GFP_OTHER_NODE is set assume the node of the preferred
    * zone is the local node. This is useful for daemons who allocate
    * memory on behalf of other processes.
    */
   void zone_statistics(struct zone *preferred_zone, struct zone *z, gfp_t flags)
   {
           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 == ((flags & __GFP_OTHER_NODE) ?
                           preferred_zone->node : numa_node_id()))
                   __inc_zone_state(z, NUMA_LOCAL);
           else
                   __inc_zone_state(z, NUMA_OTHER);
   }
   #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_COMPACTION)
   #include <linux/proc_fs.h>
   #include <linux/seq_file.h>
   
   static char * const migratetype_names[MIGRATE_TYPES] = {
           "Unmovable",
           "Reclaimable",
           "Movable",
           "Reserve",
   #ifdef CONFIG_CMA
           "CMA",
   #endif
           "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);
           }
   }
   #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[] = {
           /* Zoned VM counters */
           "nr_free_pages",
           "nr_inactive_anon",
           "nr_active_anon",
           "nr_inactive_file",
           "nr_active_file",
           "nr_unevictable",
           "nr_mlock",
           "nr_anon_pages",
           "nr_mapped",
           "nr_file_pages",
           "nr_dirty",
           "nr_writeback",
           "nr_slab_reclaimable",
           "nr_slab_unreclaimable",
           "nr_page_table_pages",
           "nr_kernel_stack",
           "nr_unstable",
           "nr_bounce",
           "nr_vmscan_write",
           "nr_vmscan_immediate_reclaim",
           "nr_writeback_temp",
           "nr_isolated_anon",
           "nr_isolated_file",
           "nr_shmem",
           "nr_dirtied",
           "nr_written",
   
   #ifdef CONFIG_NUMA
           "numa_hit",
           "numa_miss",
           "numa_foreign",
           "numa_interleave",
           "numa_local",
           "numa_other",
   #endif
           "nr_anon_transparent_hugepages",
           "nr_free_cma",
           "nr_dirty_threshold",
           "nr_dirty_background_threshold",
   
   #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_kswapd")
           TEXTS_FOR_ZONES("pgsteal_direct")
           TEXTS_FOR_ZONES("pgscan_kswapd")
           TEXTS_FOR_ZONES("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",
           "kswapd_skip_congestion_wait",
           "pageoutrun",
           "allocstall",
   
           "pgrotated",
   
   #ifdef CONFIG_NUMA_BALANCING
           "numa_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",
   #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_split",
           "thp_zero_page_alloc",
           "thp_zero_page_alloc_failed",
   #endif
   
   #endif /* CONFIG_VM_EVENTS_COUNTERS */
   };
   #endif /* CONFIG_PROC_FS || CONFIG_SYSFS || CONFIG_NUMA */
   
   
   #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, '\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, 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, '\n');
           }
   }
   
   /* 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, '\n');
   
           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);
   
                   /* Watch for unexpected holes punched in the memmap */
                   if (!memmap_valid_within(pfn, 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 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, "\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, 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_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);
   
           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 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,
                     "\n  pages free     %lu"
                     "\n        min      %lu"
                     "\n        low      %lu"
                     "\n        high     %lu"
                     "\n        scanned  %lu"
                     "\n        spanned  %lu"
                     "\n        present  %lu"
                     "\n        managed  %lu",
                     zone_page_state(zone, NR_FREE_PAGES),
                     min_wmark_pages(zone),
                     low_wmark_pages(zone),
                     high_wmark_pages(zone),
                     zone->pages_scanned,
                     zone->spanned_pages,
                     zone->present_pages,
                     zone->managed_pages);
  
          for (i = 0; i < NR_VM_ZONE_STAT_ITEMS; i++)
                  seq_printf(m, "\n    %-12s %lu", vmstat_text[i],
                                  zone_page_state(zone, i));
  
          seq_printf(m,
                     "\n        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,
                     ")"
                     "\n  pagesets");
          for_each_online_cpu(i) {
                  struct per_cpu_pageset *pageset;
  
                  pageset = per_cpu_ptr(zone->pageset, i);
                  seq_printf(m,
                             "\n    cpu: %i"
                             "\n              count: %i"
                             "\n              high:  %i"
                             "\n              batch: %i",
                             i,
                             pageset->pcp.count,
                             pageset->pcp.high,
                             pageset->pcp.batch);
  #ifdef CONFIG_SMP
                  seq_printf(m, "\n  vm stats threshold: %d",
                                  pageset->stat_threshold);
  #endif
          }
          seq_printf(m,
                     "\n  all_unreclaimable: %u"
                     "\n  start_pfn:         %lu"
                     "\n  inactive_ratio:    %u",
                     zone->all_unreclaimable,
                     zone->zone_start_pfn,
                     zone->inactive_ratio);
          seq_putc(m, '\n');
  }
  
  /*
   * 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_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;
  
          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_printf(m, "%s %lu\n", vmstat_text[off], *l);
          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 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),
                  round_jiffies_relative(sysctl_stat_interval));
  }
  
  static void __cpuinit start_cpu_timer(int cpu)
  {
          struct delayed_work *work = &per_cpu(vmstat_work, cpu);
  
          INIT_DEFERRABLE_WORK(work, vmstat_update);
          schedule_delayed_work_on(cpu, work, __round_jiffies_relative(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:
                  refresh_zone_stat_thresholds();
                  start_cpu_timer(cpu);
                  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));
                  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 };
  #endif
  
  static int __init setup_vmstat(void)
  {
  #ifdef CONFIG_SMP
          int cpu;
  
          register_cpu_notifier(&vmstat_notifier);
  
          for_each_online_cpu(cpu)
                  start_cpu_timer(cpu);
  #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)
  #include <linux/debugfs.h>
  
  
  /*
   * 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, '\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, 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, '\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, 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

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