include/linux/compaction.h

   1 #ifndef _LINUX_COMPACTION_H
   2 #define _LINUX_COMPACTION_H
   3
   4 /*
   5  * Determines how hard direct compaction should try to succeed.
   6  * Lower value means higher priority, analogically to reclaim priority.
   7  */
   8 enum compact_priority {
   9         COMPACT_PRIO_SYNC_LIGHT,
  10         MIN_COMPACT_PRIORITY = COMPACT_PRIO_SYNC_LIGHT,
  11         DEF_COMPACT_PRIORITY = COMPACT_PRIO_SYNC_LIGHT,
  12         COMPACT_PRIO_ASYNC,
  13         INIT_COMPACT_PRIORITY = COMPACT_PRIO_ASYNC
  14 };
  15
  16 /* Return values for compact_zone() and try_to_compact_pages() */
  17 /* When adding new states, please adjust include/trace/events/compaction.h */
  18 enum compact_result {
  19         /* For more detailed tracepoint output - internal to compaction */
  20         COMPACT_NOT_SUITABLE_ZONE,
  21         /*
  22          * compaction didn't start as it was not possible or direct reclaim
  23          * was more suitable
  24          */
  25         COMPACT_SKIPPED,
  26         /* compaction didn't start as it was deferred due to past failures */
  27         COMPACT_DEFERRED,
  28
  29         /* compaction not active last round */
  30         COMPACT_INACTIVE = COMPACT_DEFERRED,
  31
  32         /* For more detailed tracepoint output - internal to compaction */
  33         COMPACT_NO_SUITABLE_PAGE,
  34         /* compaction should continue to another pageblock */
  35         COMPACT_CONTINUE,
  36
  37         /*
  38          * The full zone was compacted scanned but wasn't successfull to compact
  39          * suitable pages.
  40          */
  41         COMPACT_COMPLETE,
  42         /*
  43          * direct compaction has scanned part of the zone but wasn't successfull
  44          * to compact suitable pages.
  45          */
  46         COMPACT_PARTIAL_SKIPPED,
  47
  48         /* compaction terminated prematurely due to lock contentions */
  49         COMPACT_CONTENDED,
  50
  51         /*
  52          * direct compaction terminated after concluding that the allocation
  53          * should now succeed
  54          */
  55         COMPACT_SUCCESS,
  56 };
  57
  58 struct alloc_context; /* in mm/internal.h */
  59
  60 #ifdef CONFIG_COMPACTION
  61 extern int sysctl_compact_memory;
  62 extern int sysctl_compaction_handler(struct ctl_table *table, int write,
  63                         void __user *buffer, size_t *length, loff_t *ppos);
  64 extern int sysctl_extfrag_threshold;
  65 extern int sysctl_extfrag_handler(struct ctl_table *table, int write,
  66                         void __user *buffer, size_t *length, loff_t *ppos);
  67 extern int sysctl_compact_unevictable_allowed;
  68
  69 extern int fragmentation_index(struct zone *zone, unsigned int order);
  70 extern enum compact_result try_to_compact_pages(gfp_t gfp_mask,
  71                 unsigned int order, unsigned int alloc_flags,
  72                 const struct alloc_context *ac, enum compact_priority prio);
  73 extern void reset_isolation_suitable(pg_data_t *pgdat);
  74 extern enum compact_result compaction_suitable(struct zone *zone, int order,
  75                 unsigned int alloc_flags, int classzone_idx);
  76
  77 extern void defer_compaction(struct zone *zone, int order);
  78 extern bool compaction_deferred(struct zone *zone, int order);
  79 extern void compaction_defer_reset(struct zone *zone, int order,
  80                                 bool alloc_success);
  81 extern bool compaction_restarting(struct zone *zone, int order);
  82
  83 /* Compaction has made some progress and retrying makes sense */
  84 static inline bool compaction_made_progress(enum compact_result result)
  85 {
  86         /*
  87          * Even though this might sound confusing this in fact tells us
  88          * that the compaction successfully isolated and migrated some
  89          * pageblocks.
  90          */
  91         if (result == COMPACT_SUCCESS)
  92                 return true;
  93
  94         return false;
  95 }
  96
  97 /* Compaction has failed and it doesn't make much sense to keep retrying. */
  98 static inline bool compaction_failed(enum compact_result result)
  99 {
 100         /* All zones were scanned completely and still not result. */
 101         if (result == COMPACT_COMPLETE)
 102                 return true;
 103
 104         return false;
 105 }
 106
 107 /*
 108  * Compaction  has backed off for some reason. It might be throttling or
 109  * lock contention. Retrying is still worthwhile.
 110  */
 111 static inline bool compaction_withdrawn(enum compact_result result)
 112 {
 113         /*
 114          * Compaction backed off due to watermark checks for order-0
 115          * so the regular reclaim has to try harder and reclaim something.
 116          */
 117         if (result == COMPACT_SKIPPED)
 118                 return true;
 119
 120         /*
 121          * If compaction is deferred for high-order allocations, it is
 122          * because sync compaction recently failed. If this is the case
 123          * and the caller requested a THP allocation, we do not want
 124          * to heavily disrupt the system, so we fail the allocation
 125          * instead of entering direct reclaim.
 126          */
 127         if (result == COMPACT_DEFERRED)
 128                 return true;
 129
 130         /*
 131          * If compaction in async mode encounters contention or blocks higher
 132          * priority task we back off early rather than cause stalls.
 133          */
 134         if (result == COMPACT_CONTENDED)
 135                 return true;
 136
 137         /*
 138          * Page scanners have met but we haven't scanned full zones so this
 139          * is a back off in fact.
 140          */
 141         if (result == COMPACT_PARTIAL_SKIPPED)
 142                 return true;
 143
 144         return false;
 145 }
 146
 147
 148 bool compaction_zonelist_suitable(struct alloc_context *ac, int order,
 149                                         int alloc_flags);
 150
 151 extern int kcompactd_run(int nid);
 152 extern void kcompactd_stop(int nid);
 153 extern void wakeup_kcompactd(pg_data_t *pgdat, int order, int classzone_idx);
 154
 155 #else
 156 static inline void reset_isolation_suitable(pg_data_t *pgdat)
 157 {
 158 }
 159
 160 static inline enum compact_result compaction_suitable(struct zone *zone, int order,
 161                                         int alloc_flags, int classzone_idx)
 162 {
 163         return COMPACT_SKIPPED;
 164 }
 165
 166 static inline void defer_compaction(struct zone *zone, int order)
 167 {
 168 }
 169
 170 static inline bool compaction_deferred(struct zone *zone, int order)
 171 {
 172         return true;
 173 }
 174
 175 static inline bool compaction_made_progress(enum compact_result result)
 176 {
 177         return false;
 178 }
 179
 180 static inline bool compaction_failed(enum compact_result result)
 181 {
 182         return false;
 183 }
 184
 185 static inline bool compaction_withdrawn(enum compact_result result)
 186 {
 187         return true;
 188 }
 189
 190 static inline int kcompactd_run(int nid)
 191 {
 192         return 0;
 193 }
 194 static inline void kcompactd_stop(int nid)
 195 {
 196 }
 197
 198 static inline void wakeup_kcompactd(pg_data_t *pgdat, int order, int classzone_idx)
 199 {
 200 }
 201
 202 #endif /* CONFIG_COMPACTION */
 203
 204 #if defined(CONFIG_COMPACTION) && defined(CONFIG_SYSFS) && defined(CONFIG_NUMA)
 205 struct node;
 206 extern int compaction_register_node(struct node *node);
 207 extern void compaction_unregister_node(struct node *node);
 208
 209 #else
 210
 211 static inline int compaction_register_node(struct node *node)
 212 {
 213         return 0;
 214 }
 215
 216 static inline void compaction_unregister_node(struct node *node)
 217 {
 218 }
 219 #endif /* CONFIG_COMPACTION && CONFIG_SYSFS && CONFIG_NUMA */
 220
 221 #endif /* _LINUX_COMPACTION_H */