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, struct page **page);
  26extern int 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, struct page **page)
  79{
  80        return COMPACT_CONTINUE;
  81}
  82
  83static inline int compact_pgdat(pg_data_t *pgdat, int order)
  84{
  85        return COMPACT_CONTINUE;
  86}
  87
  88static inline void reset_isolation_suitable(pg_data_t *pgdat)
  89{
  90}
  91
  92static inline unsigned long compaction_suitable(struct zone *zone, int order)
  93{
  94        return COMPACT_SKIPPED;
  95}
  96
  97static inline void defer_compaction(struct zone *zone, int order)
  98{
  99}
 100
 101static inline bool compaction_deferred(struct zone *zone, int order)
 102{
 103        return true;
 104}
 105
 106#endif /* CONFIG_COMPACTION */
 107
 108#if defined(CONFIG_COMPACTION) && defined(CONFIG_SYSFS) && defined(CONFIG_NUMA)
 109extern int compaction_register_node(struct node *node);
 110extern void compaction_unregister_node(struct node *node);
 111
 112#else
 113
 114static inline int compaction_register_node(struct node *node)
 115{
 116        return 0;
 117}
 118
 119static inline void compaction_unregister_node(struct node *node)
 120{
 121}
 122#endif /* CONFIG_COMPACTION && CONFIG_SYSFS && CONFIG_NUMA */
 123
 124#endif /* _LINUX_COMPACTION_H */
 125
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