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 partially compacted a zone and there might be
  53          * suitable pages
  54          */
  55         COMPACT_PARTIAL,
  56 };
  57
  58 /* Used to signal whether compaction detected need_sched() or lock contention */
  59 /* No contention detected */
  60 #define COMPACT_CONTENDED_NONE  0
  61 /* Either need_sched() was true or fatal signal pending */
  62 #define COMPACT_CONTENDED_SCHED 1
  63 /* Zone lock or lru_lock was contended in async compaction */
  64 #define COMPACT_CONTENDED_LOCK  2
  65
  66 struct alloc_context; /* in mm/internal.h */
  67
  68 #ifdef CONFIG_COMPACTION
  69 extern int sysctl_compact_memory;
  70 extern int sysctl_compaction_handler(struct ctl_table *table, int write,
  71                         void __user *buffer, size_t *length, loff_t *ppos);
  72 extern int sysctl_extfrag_threshold;
  73 extern int sysctl_extfrag_handler(struct ctl_table *table, int write,
  74                         void __user *buffer, size_t *length, loff_t *ppos);
  75 extern int sysctl_compact_unevictable_allowed;
  76
  77 extern int fragmentation_index(struct zone *zone, unsigned int order);
  78 extern enum compact_result try_to_compact_pages(gfp_t gfp_mask,
  79                         unsigned int order,
  80                 unsigned int alloc_flags, const struct alloc_context *ac,
  81                 enum compact_priority prio, int *contended);
  82 extern void compact_pgdat(pg_data_t *pgdat, int order);
  83 extern void reset_isolation_suitable(pg_data_t *pgdat);
  84 extern enum compact_result compaction_suitable(struct zone *zone, int order,
  85                 unsigned int alloc_flags, int classzone_idx);
  86
  87 extern void defer_compaction(struct zone *zone, int order);
  88 extern bool compaction_deferred(struct zone *zone, int order);
  89 extern void compaction_defer_reset(struct zone *zone, int order,
  90                                 bool alloc_success);
  91 extern bool compaction_restarting(struct zone *zone, int order);
  92
  93 /* Compaction has made some progress and retrying makes sense */
  94 static inline bool compaction_made_progress(enum compact_result result)
  95 {
  96         /*
  97          * Even though this might sound confusing this in fact tells us
  98          * that the compaction successfully isolated and migrated some
  99          * pageblocks.
 100          */
 101         if (result == COMPACT_PARTIAL)
 102                 return true;
 103
 104         return false;
 105 }
 106
 107 /* Compaction has failed and it doesn't make much sense to keep retrying. */
 108 static inline bool compaction_failed(enum compact_result result)
 109 {
 110         /* All zones were scanned completely and still not result. */
 111         if (result == COMPACT_COMPLETE)
 112                 return true;
 113
 114         return false;
 115 }
 116
 117 /*
 118  * Compaction  has backed off for some reason. It might be throttling or
 119  * lock contention. Retrying is still worthwhile.
 120  */
 121 static inline bool compaction_withdrawn(enum compact_result result)
 122 {
 123         /*
 124          * Compaction backed off due to watermark checks for order-0
 125          * so the regular reclaim has to try harder and reclaim something.
 126          */
 127         if (result == COMPACT_SKIPPED)
 128                 return true;
 129
 130         /*
 131          * If compaction is deferred for high-order allocations, it is
 132          * because sync compaction recently failed. If this is the case
 133          * and the caller requested a THP allocation, we do not want
 134          * to heavily disrupt the system, so we fail the allocation
 135          * instead of entering direct reclaim.
 136          */
 137         if (result == COMPACT_DEFERRED)
 138                 return true;
 139
 140         /*
 141          * If compaction in async mode encounters contention or blocks higher
 142          * priority task we back off early rather than cause stalls.
 143          */
 144         if (result == COMPACT_CONTENDED)
 145                 return true;
 146
 147         /*
 148          * Page scanners have met but we haven't scanned full zones so this
 149          * is a back off in fact.
 150          */
 151         if (result == COMPACT_PARTIAL_SKIPPED)
 152                 return true;
 153
 154         return false;
 155 }
 156
 157
 158 bool compaction_zonelist_suitable(struct alloc_context *ac, int order,
 159                                         int alloc_flags);
 160
 161 extern int kcompactd_run(int nid);
 162 extern void kcompactd_stop(int nid);
 163 extern void wakeup_kcompactd(pg_data_t *pgdat, int order, int classzone_idx);
 164
 165 #else
 166 static inline void compact_pgdat(pg_data_t *pgdat, int order)
 167 {
 168 }
 169
 170 static inline void reset_isolation_suitable(pg_data_t *pgdat)
 171 {
 172 }
 173
 174 static inline enum compact_result compaction_suitable(struct zone *zone, int order,
 175                                         int alloc_flags, int classzone_idx)
 176 {
 177         return COMPACT_SKIPPED;
 178 }
 179
 180 static inline void defer_compaction(struct zone *zone, int order)
 181 {
 182 }
 183
 184 static inline bool compaction_deferred(struct zone *zone, int order)
 185 {
 186         return true;
 187 }
 188
 189 static inline bool compaction_made_progress(enum compact_result result)
 190 {
 191         return false;
 192 }
 193
 194 static inline bool compaction_failed(enum compact_result result)
 195 {
 196         return false;
 197 }
 198
 199 static inline bool compaction_withdrawn(enum compact_result result)
 200 {
 201         return true;
 202 }
 203
 204 static inline int kcompactd_run(int nid)
 205 {
 206         return 0;
 207 }
 208 static inline void kcompactd_stop(int nid)
 209 {
 210 }
 211
 212 static inline void wakeup_kcompactd(pg_data_t *pgdat, int order, int classzone_idx)
 213 {
 214 }
 215
 216 #endif /* CONFIG_COMPACTION */
 217
 218 #if defined(CONFIG_COMPACTION) && defined(CONFIG_SYSFS) && defined(CONFIG_NUMA)
 219 struct node;
 220 extern int compaction_register_node(struct node *node);
 221 extern void compaction_unregister_node(struct node *node);
 222
 223 #else
 224
 225 static inline int compaction_register_node(struct node *node)
 226 {
 227         return 0;
 228 }
 229
 230 static inline void compaction_unregister_node(struct node *node)
 231 {
 232 }
 233 #endif /* CONFIG_COMPACTION && CONFIG_SYSFS && CONFIG_NUMA */
 234
 235 #endif /* _LINUX_COMPACTION_H */