linux/include/linux/compaction.h
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   1#ifndef _LINUX_COMPACTION_H
   2#define _LINUX_COMPACTION_H
   3
   4/* Return values for compact_zone() and try_to_compact_pages() */
   5/* compaction didn't start as it was not possible or direct reclaim was more suitable */
   6#define COMPACT_SKIPPED         0
   7/* compaction should continue to another pageblock */
   8#define COMPACT_CONTINUE        1
   9/* direct compaction partially compacted a zone and there are suitable pages */
  10#define COMPACT_PARTIAL         2
  11/* The full zone was compacted */
  12#define COMPACT_COMPLETE        3
  13
  14#ifdef CONFIG_COMPACTION
  15extern int sysctl_compact_memory;
  16extern int sysctl_compaction_handler(struct ctl_table *table, int write,
  17                        void __user *buffer, size_t *length, loff_t *ppos);
  18extern int sysctl_extfrag_threshold;
  19extern int sysctl_extfrag_handler(struct ctl_table *table, int write,
  20                        void __user *buffer, size_t *length, loff_t *ppos);
  21
  22extern int fragmentation_index(struct zone *zone, unsigned int order);
  23extern unsigned long try_to_compact_pages(struct zonelist *zonelist,
  24                        int order, gfp_t gfp_mask, nodemask_t *mask,
  25                        bool sync, bool *contended);
  26extern void compact_pgdat(pg_data_t *pgdat, int order);
  27extern void reset_isolation_suitable(pg_data_t *pgdat);
  28extern unsigned long compaction_suitable(struct zone *zone, int order);
  29
  30/* Do not skip compaction more than 64 times */
  31#define COMPACT_MAX_DEFER_SHIFT 6
  32
  33/*
  34 * Compaction is deferred when compaction fails to result in a page
  35 * allocation success. 1 << compact_defer_limit compactions are skipped up
  36 * to a limit of 1 << COMPACT_MAX_DEFER_SHIFT
  37 */
  38static inline void defer_compaction(struct zone *zone, int order)
  39{
  40        zone->compact_considered = 0;
  41        zone->compact_defer_shift++;
  42
  43        if (order < zone->compact_order_failed)
  44                zone->compact_order_failed = order;
  45
  46        if (zone->compact_defer_shift > COMPACT_MAX_DEFER_SHIFT)
  47                zone->compact_defer_shift = COMPACT_MAX_DEFER_SHIFT;
  48}
  49
  50/* Returns true if compaction should be skipped this time */
  51static inline bool compaction_deferred(struct zone *zone, int order)
  52{
  53        unsigned long defer_limit = 1UL << zone->compact_defer_shift;
  54
  55        if (order < zone->compact_order_failed)
  56                return false;
  57
  58        /* Avoid possible overflow */
  59        if (++zone->compact_considered > defer_limit)
  60                zone->compact_considered = defer_limit;
  61
  62        return zone->compact_considered < defer_limit;
  63}
  64
  65/* Returns true if restarting compaction after many failures */
  66static inline bool compaction_restarting(struct zone *zone, int order)
  67{
  68        if (order < zone->compact_order_failed)
  69                return false;
  70
  71        return zone->compact_defer_shift == COMPACT_MAX_DEFER_SHIFT &&
  72                zone->compact_considered >= 1UL << zone->compact_defer_shift;
  73}
  74
  75#else
  76static inline unsigned long try_to_compact_pages(struct zonelist *zonelist,
  77                        int order, gfp_t gfp_mask, nodemask_t *nodemask,
  78                        bool sync, bool *contended)
  79{
  80        return COMPACT_CONTINUE;
  81}
  82
  83static inline void compact_pgdat(pg_data_t *pgdat, int order)
  84{
  85}
  86
  87static inline void reset_isolation_suitable(pg_data_t *pgdat)
  88{
  89}
  90
  91static inline unsigned long compaction_suitable(struct zone *zone, int order)
  92{
  93        return COMPACT_SKIPPED;
  94}
  95
  96static inline void defer_compaction(struct zone *zone, int order)
  97{
  98}
  99
 100static inline bool compaction_deferred(struct zone *zone, int order)
 101{
 102        return true;
 103}
 104
 105#endif /* CONFIG_COMPACTION */
 106
 107#if defined(CONFIG_COMPACTION) && defined(CONFIG_SYSFS) && defined(CONFIG_NUMA)
 108extern int compaction_register_node(struct node *node);
 109extern void compaction_unregister_node(struct node *node);
 110
 111#else
 112
 113static inline int compaction_register_node(struct node *node)
 114{
 115        return 0;
 116}
 117
 118static inline void compaction_unregister_node(struct node *node)
 119{
 120}
 121#endif /* CONFIG_COMPACTION && CONFIG_SYSFS && CONFIG_NUMA */
 122
 123#endif /* _LINUX_COMPACTION_H */
 124
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