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aa45484031
Ordinarily watermark checks are based on the vmstat NR_FREE_PAGES as it is cheaper than scanning a number of lists. To avoid synchronization overhead, counter deltas are maintained on a per-cpu basis and drained both periodically and when the delta is above a threshold. On large CPU systems, the difference between the estimated and real value of NR_FREE_PAGES can be very high. If NR_FREE_PAGES is much higher than number of real free page in buddy, the VM can allocate pages below min watermark, at worst reducing the real number of pages to zero. Even if the OOM killer kills some victim for freeing memory, it may not free memory if the exit path requires a new page resulting in livelock. This patch introduces a zone_page_state_snapshot() function (courtesy of Christoph) that takes a slightly more accurate view of an arbitrary vmstat counter. It is used to read NR_FREE_PAGES while kswapd is awake to avoid the watermark being accidentally broken. The estimate is not perfect and may result in cache line bounces but is expected to be lighter than the IPI calls necessary to continually drain the per-cpu counters while kswapd is awake. Signed-off-by: Christoph Lameter <cl@linux.com> Signed-off-by: Mel Gorman <mel@csn.ul.ie> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
304 lines
7.7 KiB
C
304 lines
7.7 KiB
C
#ifndef _LINUX_VMSTAT_H
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#define _LINUX_VMSTAT_H
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#include <linux/types.h>
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#include <linux/percpu.h>
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#include <linux/mm.h>
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#include <linux/mmzone.h>
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#include <asm/atomic.h>
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#ifdef CONFIG_ZONE_DMA
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#define DMA_ZONE(xx) xx##_DMA,
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#else
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#define DMA_ZONE(xx)
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#endif
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#ifdef CONFIG_ZONE_DMA32
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#define DMA32_ZONE(xx) xx##_DMA32,
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#else
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#define DMA32_ZONE(xx)
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#endif
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#ifdef CONFIG_HIGHMEM
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#define HIGHMEM_ZONE(xx) , xx##_HIGH
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#else
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#define HIGHMEM_ZONE(xx)
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#endif
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#define FOR_ALL_ZONES(xx) DMA_ZONE(xx) DMA32_ZONE(xx) xx##_NORMAL HIGHMEM_ZONE(xx) , xx##_MOVABLE
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enum vm_event_item { PGPGIN, PGPGOUT, PSWPIN, PSWPOUT,
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FOR_ALL_ZONES(PGALLOC),
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PGFREE, PGACTIVATE, PGDEACTIVATE,
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PGFAULT, PGMAJFAULT,
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FOR_ALL_ZONES(PGREFILL),
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FOR_ALL_ZONES(PGSTEAL),
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FOR_ALL_ZONES(PGSCAN_KSWAPD),
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FOR_ALL_ZONES(PGSCAN_DIRECT),
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#ifdef CONFIG_NUMA
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PGSCAN_ZONE_RECLAIM_FAILED,
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#endif
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PGINODESTEAL, SLABS_SCANNED, KSWAPD_STEAL, KSWAPD_INODESTEAL,
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KSWAPD_LOW_WMARK_HIT_QUICKLY, KSWAPD_HIGH_WMARK_HIT_QUICKLY,
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KSWAPD_SKIP_CONGESTION_WAIT,
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PAGEOUTRUN, ALLOCSTALL, PGROTATED,
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#ifdef CONFIG_COMPACTION
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COMPACTBLOCKS, COMPACTPAGES, COMPACTPAGEFAILED,
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COMPACTSTALL, COMPACTFAIL, COMPACTSUCCESS,
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#endif
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#ifdef CONFIG_HUGETLB_PAGE
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HTLB_BUDDY_PGALLOC, HTLB_BUDDY_PGALLOC_FAIL,
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#endif
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UNEVICTABLE_PGCULLED, /* culled to noreclaim list */
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UNEVICTABLE_PGSCANNED, /* scanned for reclaimability */
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UNEVICTABLE_PGRESCUED, /* rescued from noreclaim list */
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UNEVICTABLE_PGMLOCKED,
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UNEVICTABLE_PGMUNLOCKED,
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UNEVICTABLE_PGCLEARED, /* on COW, page truncate */
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UNEVICTABLE_PGSTRANDED, /* unable to isolate on unlock */
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UNEVICTABLE_MLOCKFREED,
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NR_VM_EVENT_ITEMS
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};
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extern int sysctl_stat_interval;
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#ifdef CONFIG_VM_EVENT_COUNTERS
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/*
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* Light weight per cpu counter implementation.
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*
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* Counters should only be incremented and no critical kernel component
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* should rely on the counter values.
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*
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* Counters are handled completely inline. On many platforms the code
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* generated will simply be the increment of a global address.
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*/
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struct vm_event_state {
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unsigned long event[NR_VM_EVENT_ITEMS];
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};
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DECLARE_PER_CPU(struct vm_event_state, vm_event_states);
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static inline void __count_vm_event(enum vm_event_item item)
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{
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__this_cpu_inc(vm_event_states.event[item]);
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}
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static inline void count_vm_event(enum vm_event_item item)
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{
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this_cpu_inc(vm_event_states.event[item]);
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}
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static inline void __count_vm_events(enum vm_event_item item, long delta)
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{
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__this_cpu_add(vm_event_states.event[item], delta);
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}
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static inline void count_vm_events(enum vm_event_item item, long delta)
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{
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this_cpu_add(vm_event_states.event[item], delta);
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}
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extern void all_vm_events(unsigned long *);
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#ifdef CONFIG_HOTPLUG
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extern void vm_events_fold_cpu(int cpu);
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#else
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static inline void vm_events_fold_cpu(int cpu)
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{
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}
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#endif
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#else
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/* Disable counters */
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static inline void count_vm_event(enum vm_event_item item)
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{
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}
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static inline void count_vm_events(enum vm_event_item item, long delta)
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{
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}
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static inline void __count_vm_event(enum vm_event_item item)
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{
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}
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static inline void __count_vm_events(enum vm_event_item item, long delta)
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{
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}
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static inline void all_vm_events(unsigned long *ret)
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{
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}
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static inline void vm_events_fold_cpu(int cpu)
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{
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}
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#endif /* CONFIG_VM_EVENT_COUNTERS */
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#define __count_zone_vm_events(item, zone, delta) \
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__count_vm_events(item##_NORMAL - ZONE_NORMAL + \
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zone_idx(zone), delta)
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/*
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* Zone based page accounting with per cpu differentials.
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*/
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extern atomic_long_t vm_stat[NR_VM_ZONE_STAT_ITEMS];
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static inline void zone_page_state_add(long x, struct zone *zone,
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enum zone_stat_item item)
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{
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atomic_long_add(x, &zone->vm_stat[item]);
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atomic_long_add(x, &vm_stat[item]);
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}
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static inline unsigned long global_page_state(enum zone_stat_item item)
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{
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long x = atomic_long_read(&vm_stat[item]);
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#ifdef CONFIG_SMP
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if (x < 0)
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x = 0;
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#endif
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return x;
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}
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static inline unsigned long zone_page_state(struct zone *zone,
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enum zone_stat_item item)
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{
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long x = atomic_long_read(&zone->vm_stat[item]);
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#ifdef CONFIG_SMP
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if (x < 0)
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x = 0;
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#endif
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return x;
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}
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/*
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* More accurate version that also considers the currently pending
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* deltas. For that we need to loop over all cpus to find the current
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* deltas. There is no synchronization so the result cannot be
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* exactly accurate either.
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*/
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static inline unsigned long zone_page_state_snapshot(struct zone *zone,
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enum zone_stat_item item)
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{
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long x = atomic_long_read(&zone->vm_stat[item]);
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#ifdef CONFIG_SMP
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int cpu;
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for_each_online_cpu(cpu)
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x += per_cpu_ptr(zone->pageset, cpu)->vm_stat_diff[item];
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if (x < 0)
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x = 0;
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#endif
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return x;
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}
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extern unsigned long global_reclaimable_pages(void);
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extern unsigned long zone_reclaimable_pages(struct zone *zone);
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#ifdef CONFIG_NUMA
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/*
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* Determine the per node value of a stat item. This function
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* is called frequently in a NUMA machine, so try to be as
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* frugal as possible.
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*/
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static inline unsigned long node_page_state(int node,
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enum zone_stat_item item)
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{
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struct zone *zones = NODE_DATA(node)->node_zones;
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return
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#ifdef CONFIG_ZONE_DMA
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zone_page_state(&zones[ZONE_DMA], item) +
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#endif
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#ifdef CONFIG_ZONE_DMA32
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zone_page_state(&zones[ZONE_DMA32], item) +
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#endif
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#ifdef CONFIG_HIGHMEM
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zone_page_state(&zones[ZONE_HIGHMEM], item) +
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#endif
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zone_page_state(&zones[ZONE_NORMAL], item) +
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zone_page_state(&zones[ZONE_MOVABLE], item);
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}
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extern void zone_statistics(struct zone *, struct zone *);
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#else
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#define node_page_state(node, item) global_page_state(item)
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#define zone_statistics(_zl,_z) do { } while (0)
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#endif /* CONFIG_NUMA */
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#define add_zone_page_state(__z, __i, __d) mod_zone_page_state(__z, __i, __d)
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#define sub_zone_page_state(__z, __i, __d) mod_zone_page_state(__z, __i, -(__d))
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static inline void zap_zone_vm_stats(struct zone *zone)
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{
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memset(zone->vm_stat, 0, sizeof(zone->vm_stat));
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}
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extern void inc_zone_state(struct zone *, enum zone_stat_item);
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#ifdef CONFIG_SMP
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void __mod_zone_page_state(struct zone *, enum zone_stat_item item, int);
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void __inc_zone_page_state(struct page *, enum zone_stat_item);
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void __dec_zone_page_state(struct page *, enum zone_stat_item);
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void mod_zone_page_state(struct zone *, enum zone_stat_item, int);
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void inc_zone_page_state(struct page *, enum zone_stat_item);
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void dec_zone_page_state(struct page *, enum zone_stat_item);
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extern void inc_zone_state(struct zone *, enum zone_stat_item);
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extern void __inc_zone_state(struct zone *, enum zone_stat_item);
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extern void dec_zone_state(struct zone *, enum zone_stat_item);
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extern void __dec_zone_state(struct zone *, enum zone_stat_item);
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void refresh_cpu_vm_stats(int);
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#else /* CONFIG_SMP */
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/*
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* We do not maintain differentials in a single processor configuration.
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* The functions directly modify the zone and global counters.
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*/
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static inline void __mod_zone_page_state(struct zone *zone,
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enum zone_stat_item item, int delta)
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{
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zone_page_state_add(delta, zone, item);
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}
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static inline void __inc_zone_state(struct zone *zone, enum zone_stat_item item)
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{
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atomic_long_inc(&zone->vm_stat[item]);
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atomic_long_inc(&vm_stat[item]);
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}
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static inline void __inc_zone_page_state(struct page *page,
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enum zone_stat_item item)
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{
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__inc_zone_state(page_zone(page), item);
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}
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static inline void __dec_zone_state(struct zone *zone, enum zone_stat_item item)
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{
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atomic_long_dec(&zone->vm_stat[item]);
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atomic_long_dec(&vm_stat[item]);
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}
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static inline void __dec_zone_page_state(struct page *page,
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enum zone_stat_item item)
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{
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__dec_zone_state(page_zone(page), item);
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}
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/*
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* We only use atomic operations to update counters. So there is no need to
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* disable interrupts.
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*/
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#define inc_zone_page_state __inc_zone_page_state
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#define dec_zone_page_state __dec_zone_page_state
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#define mod_zone_page_state __mod_zone_page_state
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static inline void refresh_cpu_vm_stats(int cpu) { }
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#endif
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#endif /* _LINUX_VMSTAT_H */
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