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_FULL,
  10         MIN_COMPACT_PRIORITY = COMPACT_PRIO_SYNC_FULL,
  11         COMPACT_PRIO_SYNC_LIGHT,
  12         MIN_COMPACT_COSTLY_PRIORITY = COMPACT_PRIO_SYNC_LIGHT,
  13         DEF_COMPACT_PRIORITY = COMPACT_PRIO_SYNC_LIGHT,
  14         COMPACT_PRIO_ASYNC,
  15         INIT_COMPACT_PRIORITY = COMPACT_PRIO_ASYNC
  16 };
  17
  18 /* Return values for compact_zone() and try_to_compact_pages() */
  19 /* When adding new states, please adjust include/trace/events/compaction.h */
  20 enum compact_result {
  21         /* For more detailed tracepoint output - internal to compaction */
  22         COMPACT_NOT_SUITABLE_ZONE,
  23         /*
  24          * compaction didn't start as it was not possible or direct reclaim
  25          * was more suitable
  26          */
  27         COMPACT_SKIPPED,
  28         /* compaction didn't start as it was deferred due to past failures */
  29         COMPACT_DEFERRED,
  30
  31         /* compaction not active last round */
  32         COMPACT_INACTIVE = COMPACT_DEFERRED,
  33
  34         /* For more detailed tracepoint output - internal to compaction */
  35         COMPACT_NO_SUITABLE_PAGE,
  36         /* compaction should continue to another pageblock */
  37         COMPACT_CONTINUE,
  38
  39         /*
  40          * The full zone was compacted scanned but wasn't successfull to compact
  41          * suitable pages.
  42          */
  43         COMPACT_COMPLETE,
  44         /*
  45          * direct compaction has scanned part of the zone but wasn't successfull
  46          * to compact suitable pages.
  47          */
  48         COMPACT_PARTIAL_SKIPPED,
  49
  50         /* compaction terminated prematurely due to lock contentions */
  51         COMPACT_CONTENDED,
  52
  53         /*
  54          * direct compaction terminated after concluding that the allocation
  55          * should now succeed
  56          */
  57         COMPACT_SUCCESS,
  58 };
  59
  60 struct alloc_context; /* in mm/internal.h */
  61
  62 /*
  63  * Number of free order-0 pages that should be available above given watermark
  64  * to make sure compaction has reasonable chance of not running out of free
  65  * pages that it needs to isolate as migration target during its work.
  66  */
  67 static inline unsigned long compact_gap(unsigned int order)
  68 {
  69         /*
  70          * Although all the isolations for migration are temporary, compaction
  71          * free scanner may have up to 1 << order pages on its list and then
  72          * try to split an (order - 1) free page. At that point, a gap of
  73          * 1 << order might not be enough, so it's safer to require twice that
  74          * amount. Note that the number of pages on the list is also
  75          * effectively limited by COMPACT_CLUSTER_MAX, as that's the maximum
  76          * that the migrate scanner can have isolated on migrate list, and free
  77          * scanner is only invoked when the number of isolated free pages is
  78          * lower than that. But it's not worth to complicate the formula here
  79          * as a bigger gap for higher orders than strictly necessary can also
  80          * improve chances of compaction success.
  81          */
  82         return 2UL << order;
  83 }
  84
  85 #ifdef CONFIG_COMPACTION
  86 extern int sysctl_compact_memory;
  87 extern int sysctl_compaction_handler(struct ctl_table *table, int write,
  88                         void __user *buffer, size_t *length, loff_t *ppos);
  89 extern int sysctl_extfrag_threshold;
  90 extern int sysctl_extfrag_handler(struct ctl_table *table, int write,
  91                         void __user *buffer, size_t *length, loff_t *ppos);
  92 extern int sysctl_compact_unevictable_allowed;
  93
  94 extern int fragmentation_index(struct zone *zone, unsigned int order);
  95 extern enum compact_result try_to_compact_pages(gfp_t gfp_mask,
  96                 unsigned int order, unsigned int alloc_flags,
  97                 const struct alloc_context *ac, enum compact_priority prio);
  98 extern void reset_isolation_suitable(pg_data_t *pgdat);
  99 extern enum compact_result compaction_suitable(struct zone *zone, int order,
 100                 unsigned int alloc_flags, int classzone_idx);
 101
 102 extern void defer_compaction(struct zone *zone, int order);
 103 extern bool compaction_deferred(struct zone *zone, int order);
 104 extern void compaction_defer_reset(struct zone *zone, int order,
 105                                 bool alloc_success);
 106 extern bool compaction_restarting(struct zone *zone, int order);
 107
 108 /* Compaction has made some progress and retrying makes sense */
 109 static inline bool compaction_made_progress(enum compact_result result)
 110 {
 111         /*
 112          * Even though this might sound confusing this in fact tells us
 113          * that the compaction successfully isolated and migrated some
 114          * pageblocks.
 115          */
 116         if (result == COMPACT_SUCCESS)
 117                 return true;
 118
 119         return false;
 120 }
 121
 122 /* Compaction has failed and it doesn't make much sense to keep retrying. */
 123 static inline bool compaction_failed(enum compact_result result)
 124 {
 125         /* All zones were scanned completely and still not result. */
 126         if (result == COMPACT_COMPLETE)
 127                 return true;
 128
 129         return false;
 130 }
 131
 132 /*
 133  * Compaction  has backed off for some reason. It might be throttling or
 134  * lock contention. Retrying is still worthwhile.
 135  */
 136 static inline bool compaction_withdrawn(enum compact_result result)
 137 {
 138         /*
 139          * Compaction backed off due to watermark checks for order-0
 140          * so the regular reclaim has to try harder and reclaim something.
 141          */
 142         if (result == COMPACT_SKIPPED)
 143                 return true;
 144
 145         /*
 146          * If compaction is deferred for high-order allocations, it is
 147          * because sync compaction recently failed. If this is the case
 148          * and the caller requested a THP allocation, we do not want
 149          * to heavily disrupt the system, so we fail the allocation
 150          * instead of entering direct reclaim.
 151          */
 152         if (result == COMPACT_DEFERRED)
 153                 return true;
 154
 155         /*
 156          * If compaction in async mode encounters contention or blocks higher
 157          * priority task we back off early rather than cause stalls.
 158          */
 159         if (result == COMPACT_CONTENDED)
 160                 return true;
 161
 162         /*
 163          * Page scanners have met but we haven't scanned full zones so this
 164          * is a back off in fact.
 165          */
 166         if (result == COMPACT_PARTIAL_SKIPPED)
 167                 return true;
 168
 169         return false;
 170 }
 171
 172
 173 bool compaction_zonelist_suitable(struct alloc_context *ac, int order,
 174                                         int alloc_flags);
 175
 176 extern int kcompactd_run(int nid);
 177 extern void kcompactd_stop(int nid);
 178 extern void wakeup_kcompactd(pg_data_t *pgdat, int order, int classzone_idx);
 179
 180 #else
 181 static inline void reset_isolation_suitable(pg_data_t *pgdat)
 182 {
 183 }
 184
 185 static inline enum compact_result compaction_suitable(struct zone *zone, int order,
 186                                         int alloc_flags, int classzone_idx)
 187 {
 188         return COMPACT_SKIPPED;
 189 }
 190
 191 static inline void defer_compaction(struct zone *zone, int order)
 192 {
 193 }
 194
 195 static inline bool compaction_deferred(struct zone *zone, int order)
 196 {
 197         return true;
 198 }
 199
 200 static inline bool compaction_made_progress(enum compact_result result)
 201 {
 202         return false;
 203 }
 204
 205 static inline bool compaction_failed(enum compact_result result)
 206 {
 207         return false;
 208 }
 209
 210 static inline bool compaction_withdrawn(enum compact_result result)
 211 {
 212         return true;
 213 }
 214
 215 static inline int kcompactd_run(int nid)
 216 {
 217         return 0;
 218 }
 219 static inline void kcompactd_stop(int nid)
 220 {
 221 }
 222
 223 static inline void wakeup_kcompactd(pg_data_t *pgdat, int order, int classzone_idx)
 224 {
 225 }
 226
 227 #endif /* CONFIG_COMPACTION */
 228
 229 #if defined(CONFIG_COMPACTION) && defined(CONFIG_SYSFS) && defined(CONFIG_NUMA)
 230 struct node;
 231 extern int compaction_register_node(struct node *node);
 232 extern void compaction_unregister_node(struct node *node);
 233
 234 #else
 235
 236 static inline int compaction_register_node(struct node *node)
 237 {
 238         return 0;
 239 }
 240
 241 static inline void compaction_unregister_node(struct node *node)
 242 {
 243 }
 244 #endif /* CONFIG_COMPACTION && CONFIG_SYSFS && CONFIG_NUMA */
 245
 246 #endif /* _LINUX_COMPACTION_H */