LXR linux/include/linux/compaction.h

   1#ifndef _LINUX_COMPACTION_H
   2#define _LINUX_COMPACTION_H
   3
   4/* Return values for compact_zone() and try_to_compact_pages() */
   5/* When adding new states, please adjust include/trace/events/compaction.h */
   6enum compact_result {
   7        /* For more detailed tracepoint output - internal to compaction */
   8        COMPACT_NOT_SUITABLE_ZONE,
   9        /*
  10         * compaction didn't start as it was not possible or direct reclaim
  11         * was more suitable
  12         */
  13        COMPACT_SKIPPED,
  14        /* compaction didn't start as it was deferred due to past failures */
  15        COMPACT_DEFERRED,
  16
  17        /* compaction not active last round */
  18        COMPACT_INACTIVE = COMPACT_DEFERRED,
  19
  20        /* For more detailed tracepoint output - internal to compaction */
  21        COMPACT_NO_SUITABLE_PAGE,
  22        /* compaction should continue to another pageblock */
  23        COMPACT_CONTINUE,
  24
  25        /*
  26         * The full zone was compacted scanned but wasn't successfull to compact
  27         * suitable pages.
  28         */
  29        COMPACT_COMPLETE,
  30        /*
  31         * direct compaction has scanned part of the zone but wasn't successfull
  32         * to compact suitable pages.
  33         */
  34        COMPACT_PARTIAL_SKIPPED,
  35
  36        /* compaction terminated prematurely due to lock contentions */
  37        COMPACT_CONTENDED,
  38
  39        /*
  40         * direct compaction partially compacted a zone and there might be
  41         * suitable pages
  42         */
  43        COMPACT_PARTIAL,
  44};
  45
  46/* Used to signal whether compaction detected need_sched() or lock contention */
  47/* No contention detected */
  48#define COMPACT_CONTENDED_NONE  0
  49/* Either need_sched() was true or fatal signal pending */
  50#define COMPACT_CONTENDED_SCHED 1
  51/* Zone lock or lru_lock was contended in async compaction */
  52#define COMPACT_CONTENDED_LOCK  2
  53
  54struct alloc_context; /* in mm/internal.h */
  55
  56#ifdef CONFIG_COMPACTION
  57extern int sysctl_compact_memory;
  58extern int sysctl_compaction_handler(struct ctl_table *table, int write,
  59                        void __user *buffer, size_t *length, loff_t *ppos);
  60extern int sysctl_extfrag_threshold;
  61extern int sysctl_extfrag_handler(struct ctl_table *table, int write,
  62                        void __user *buffer, size_t *length, loff_t *ppos);
  63extern int sysctl_compact_unevictable_allowed;
  64
  65extern int fragmentation_index(struct zone *zone, unsigned int order);
  66extern enum compact_result try_to_compact_pages(gfp_t gfp_mask,
  67                        unsigned int order,
  68                unsigned int alloc_flags, const struct alloc_context *ac,
  69                enum migrate_mode mode, int *contended);
  70extern void compact_pgdat(pg_data_t *pgdat, int order);
  71extern void reset_isolation_suitable(pg_data_t *pgdat);
  72extern enum compact_result compaction_suitable(struct zone *zone, int order,
  73                unsigned int alloc_flags, int classzone_idx);
  74
  75extern void defer_compaction(struct zone *zone, int order);
  76extern bool compaction_deferred(struct zone *zone, int order);
  77extern void compaction_defer_reset(struct zone *zone, int order,
  78                                bool alloc_success);
  79extern bool compaction_restarting(struct zone *zone, int order);
  80
  81/* Compaction has made some progress and retrying makes sense */
  82static inline bool compaction_made_progress(enum compact_result result)
  83{
  84        /*
  85         * Even though this might sound confusing this in fact tells us
  86         * that the compaction successfully isolated and migrated some
  87         * pageblocks.
  88         */
  89        if (result == COMPACT_PARTIAL)
  90                return true;
  91
  92        return false;
  93}
  94
  95/* Compaction has failed and it doesn't make much sense to keep retrying. */
  96static inline bool compaction_failed(enum compact_result result)
  97{
  98        /* All zones were scanned completely and still not result. */
  99        if (result == COMPACT_COMPLETE)
 100                return true;
 101
 102        return false;
 103}
 104
 105/*
 106 * Compaction  has backed off for some reason. It might be throttling or
 107 * lock contention. Retrying is still worthwhile.
 108 */
 109static inline bool compaction_withdrawn(enum compact_result result)
 110{
 111        /*
 112         * Compaction backed off due to watermark checks for order-0
 113         * so the regular reclaim has to try harder and reclaim something.
 114         */
 115        if (result == COMPACT_SKIPPED)
 116                return true;
 117
 118        /*
 119         * If compaction is deferred for high-order allocations, it is
 120         * because sync compaction recently failed. If this is the case
 121         * and the caller requested a THP allocation, we do not want
 122         * to heavily disrupt the system, so we fail the allocation
 123         * instead of entering direct reclaim.
 124         */
 125        if (result == COMPACT_DEFERRED)
 126                return true;
 127
 128        /*
 129         * If compaction in async mode encounters contention or blocks higher
 130         * priority task we back off early rather than cause stalls.
 131         */
 132        if (result == COMPACT_CONTENDED)
 133                return true;
 134
 135        /*
 136         * Page scanners have met but we haven't scanned full zones so this
 137         * is a back off in fact.
 138         */
 139        if (result == COMPACT_PARTIAL_SKIPPED)
 140                return true;
 141
 142        return false;
 143}
 144
 145
 146bool compaction_zonelist_suitable(struct alloc_context *ac, int order,
 147                                        int alloc_flags);
 148
 149extern int kcompactd_run(int nid);
 150extern void kcompactd_stop(int nid);
 151extern void wakeup_kcompactd(pg_data_t *pgdat, int order, int classzone_idx);
 152
 153#else
 154static inline enum compact_result try_to_compact_pages(gfp_t gfp_mask,
 155                        unsigned int order, int alloc_flags,
 156                        const struct alloc_context *ac,
 157                        enum migrate_mode mode, int *contended)
 158{
 159        return COMPACT_CONTINUE;
 160}
 161
 162static inline void compact_pgdat(pg_data_t *pgdat, int order)
 163{
 164}
 165
 166static inline void reset_isolation_suitable(pg_data_t *pgdat)
 167{
 168}
 169
 170static inline enum compact_result compaction_suitable(struct zone *zone, int order,
 171                                        int alloc_flags, int classzone_idx)
 172{
 173        return COMPACT_SKIPPED;
 174}
 175
 176static inline void defer_compaction(struct zone *zone, int order)
 177{
 178}
 179
 180static inline bool compaction_deferred(struct zone *zone, int order)
 181{
 182        return true;
 183}
 184
 185static inline bool compaction_made_progress(enum compact_result result)
 186{
 187        return false;
 188}
 189
 190static inline bool compaction_failed(enum compact_result result)
 191{
 192        return false;
 193}
 194
 195static inline bool compaction_withdrawn(enum compact_result result)
 196{
 197        return true;
 198}
 199
 200static inline int kcompactd_run(int nid)
 201{
 202        return 0;
 203}
 204static inline void kcompactd_stop(int nid)
 205{
 206}
 207
 208static inline void wakeup_kcompactd(pg_data_t *pgdat, int order, int classzone_idx)
 209{
 210}
 211
 212#endif /* CONFIG_COMPACTION */
 213
 214#if defined(CONFIG_COMPACTION) && defined(CONFIG_SYSFS) && defined(CONFIG_NUMA)
 215extern int compaction_register_node(struct node *node);
 216extern void compaction_unregister_node(struct node *node);
 217
 218#else
 219
 220static inline int compaction_register_node(struct node *node)
 221{
 222        return 0;
 223}
 224
 225static inline void compaction_unregister_node(struct node *node)
 226{
 227}
 228#endif /* CONFIG_COMPACTION && CONFIG_SYSFS && CONFIG_NUMA */
 229
 230#endif /* _LINUX_COMPACTION_H */
 231