include/linux/compaction.h

   1 /* SPDX-License-Identifier: GPL-2.0 */
   2 #ifndef _LINUX_COMPACTION_H
   3 #define _LINUX_COMPACTION_H
   4
   5 /*
   6  * Determines how hard direct compaction should try to succeed.
   7  * Lower value means higher priority, analogically to reclaim priority.
   8  */
   9 enum compact_priority {
  10         COMPACT_PRIO_SYNC_FULL,
  11         MIN_COMPACT_PRIORITY = COMPACT_PRIO_SYNC_FULL,
  12         COMPACT_PRIO_SYNC_LIGHT,
  13         MIN_COMPACT_COSTLY_PRIORITY = COMPACT_PRIO_SYNC_LIGHT,
  14         DEF_COMPACT_PRIORITY = COMPACT_PRIO_SYNC_LIGHT,
  15         COMPACT_PRIO_ASYNC,
  16         INIT_COMPACT_PRIORITY = COMPACT_PRIO_ASYNC
  17 };
  18
  19 /* Return values for compact_zone() and try_to_compact_pages() */
  20 /* When adding new states, please adjust include/trace/events/compaction.h */
  21 enum compact_result {
  22         /* For more detailed tracepoint output - internal to compaction */
  23         COMPACT_NOT_SUITABLE_ZONE,
  24         /*
  25          * compaction didn't start as it was not possible or direct reclaim
  26          * was more suitable
  27          */
  28         COMPACT_SKIPPED,
  29         /* compaction didn't start as it was deferred due to past failures */
  30         COMPACT_DEFERRED,
  31
  32         /* compaction not active last round */
  33         COMPACT_INACTIVE = COMPACT_DEFERRED,
  34
  35         /* For more detailed tracepoint output - internal to compaction */
  36         COMPACT_NO_SUITABLE_PAGE,
  37         /* compaction should continue to another pageblock */
  38         COMPACT_CONTINUE,
  39
  40         /*
  41          * The full zone was compacted scanned but wasn't successfull to compact
  42          * suitable pages.
  43          */
  44         COMPACT_COMPLETE,
  45         /*
  46          * direct compaction has scanned part of the zone but wasn't successfull
  47          * to compact suitable pages.
  48          */
  49         COMPACT_PARTIAL_SKIPPED,
  50
  51         /* compaction terminated prematurely due to lock contentions */
  52         COMPACT_CONTENDED,
  53
  54         /*
  55          * direct compaction terminated after concluding that the allocation
  56          * should now succeed
  57          */
  58         COMPACT_SUCCESS,
  59 };
  60
  61 struct alloc_context; /* in mm/internal.h */
  62
  63 /*
  64  * Number of free order-0 pages that should be available above given watermark
  65  * to make sure compaction has reasonable chance of not running out of free
  66  * pages that it needs to isolate as migration target during its work.
  67  */
  68 static inline unsigned long compact_gap(unsigned int order)
  69 {
  70         /*
  71          * Although all the isolations for migration are temporary, compaction
  72          * free scanner may have up to 1 << order pages on its list and then
  73          * try to split an (order - 1) free page. At that point, a gap of
  74          * 1 << order might not be enough, so it's safer to require twice that
  75          * amount. Note that the number of pages on the list is also
  76          * effectively limited by COMPACT_CLUSTER_MAX, as that's the maximum
  77          * that the migrate scanner can have isolated on migrate list, and free
  78          * scanner is only invoked when the number of isolated free pages is
  79          * lower than that. But it's not worth to complicate the formula here
  80          * as a bigger gap for higher orders than strictly necessary can also
  81          * improve chances of compaction success.
  82          */
  83         return 2UL << order;
  84 }
  85
  86 #ifdef CONFIG_COMPACTION
  87 extern int sysctl_compact_memory;
  88 extern int sysctl_compaction_handler(struct ctl_table *table, int write,
  89                         void __user *buffer, size_t *length, loff_t *ppos);
  90 extern int sysctl_extfrag_threshold;
  91 extern int sysctl_extfrag_handler(struct ctl_table *table, int write,
  92                         void __user *buffer, size_t *length, loff_t *ppos);
  93 extern int sysctl_compact_unevictable_allowed;
  94
  95 extern int fragmentation_index(struct zone *zone, unsigned int order);
  96 extern enum compact_result try_to_compact_pages(gfp_t gfp_mask,
  97                 unsigned int order, unsigned int alloc_flags,
  98                 const struct alloc_context *ac, enum compact_priority prio);
  99 extern void reset_isolation_suitable(pg_data_t *pgdat);
 100 extern enum compact_result compaction_suitable(struct zone *zone, int order,
 101                 unsigned int alloc_flags, int classzone_idx);
 102
 103 extern void defer_compaction(struct zone *zone, int order);
 104 extern bool compaction_deferred(struct zone *zone, int order);
 105 extern void compaction_defer_reset(struct zone *zone, int order,
 106                                 bool alloc_success);
 107 extern bool compaction_restarting(struct zone *zone, int order);
 108
 109 /* Compaction has made some progress and retrying makes sense */
 110 static inline bool compaction_made_progress(enum compact_result result)
 111 {
 112         /*
 113          * Even though this might sound confusing this in fact tells us
 114          * that the compaction successfully isolated and migrated some
 115          * pageblocks.
 116          */
 117         if (result == COMPACT_SUCCESS)
 118                 return true;
 119
 120         return false;
 121 }
 122
 123 /* Compaction has failed and it doesn't make much sense to keep retrying. */
 124 static inline bool compaction_failed(enum compact_result result)
 125 {
 126         /* All zones were scanned completely and still not result. */
 127         if (result == COMPACT_COMPLETE)
 128                 return true;
 129
 130         return false;
 131 }
 132
 133 /*
 134  * Compaction  has backed off for some reason. It might be throttling or
 135  * lock contention. Retrying is still worthwhile.
 136  */
 137 static inline bool compaction_withdrawn(enum compact_result result)
 138 {
 139         /*
 140          * Compaction backed off due to watermark checks for order-0
 141          * so the regular reclaim has to try harder and reclaim something.
 142          */
 143         if (result == COMPACT_SKIPPED)
 144                 return true;
 145
 146         /*
 147          * If compaction is deferred for high-order allocations, it is
 148          * because sync compaction recently failed. If this is the case
 149          * and the caller requested a THP allocation, we do not want
 150          * to heavily disrupt the system, so we fail the allocation
 151          * instead of entering direct reclaim.
 152          */
 153         if (result == COMPACT_DEFERRED)
 154                 return true;
 155
 156         /*
 157          * If compaction in async mode encounters contention or blocks higher
 158          * priority task we back off early rather than cause stalls.
 159          */
 160         if (result == COMPACT_CONTENDED)
 161                 return true;
 162
 163         /*
 164          * Page scanners have met but we haven't scanned full zones so this
 165          * is a back off in fact.
 166          */
 167         if (result == COMPACT_PARTIAL_SKIPPED)
 168                 return true;
 169
 170         return false;
 171 }
 172
 173
 174 bool compaction_zonelist_suitable(struct alloc_context *ac, int order,
 175                                         int alloc_flags);
 176
 177 extern int kcompactd_run(int nid);
 178 extern void kcompactd_stop(int nid);
 179 extern void wakeup_kcompactd(pg_data_t *pgdat, int order, int classzone_idx);
 180
 181 #else
 182 static inline void reset_isolation_suitable(pg_data_t *pgdat)
 183 {
 184 }
 185
 186 static inline enum compact_result compaction_suitable(struct zone *zone, int order,
 187                                         int alloc_flags, int classzone_idx)
 188 {
 189         return COMPACT_SKIPPED;
 190 }
 191
 192 static inline void defer_compaction(struct zone *zone, int order)
 193 {
 194 }
 195
 196 static inline bool compaction_deferred(struct zone *zone, int order)
 197 {
 198         return true;
 199 }
 200
 201 static inline bool compaction_made_progress(enum compact_result result)
 202 {
 203         return false;
 204 }
 205
 206 static inline bool compaction_failed(enum compact_result result)
 207 {
 208         return false;
 209 }
 210
 211 static inline bool compaction_withdrawn(enum compact_result result)
 212 {
 213         return true;
 214 }
 215
 216 static inline int kcompactd_run(int nid)
 217 {
 218         return 0;
 219 }
 220 static inline void kcompactd_stop(int nid)
 221 {
 222 }
 223
 224 static inline void wakeup_kcompactd(pg_data_t *pgdat, int order, int classzone_idx)
 225 {
 226 }
 227
 228 #endif /* CONFIG_COMPACTION */
 229
 230 #if defined(CONFIG_COMPACTION) && defined(CONFIG_SYSFS) && defined(CONFIG_NUMA)
 231 struct node;
 232 extern int compaction_register_node(struct node *node);
 233 extern void compaction_unregister_node(struct node *node);
 234
 235 #else
 236
 237 static inline int compaction_register_node(struct node *node)
 238 {
 239         return 0;
 240 }
 241
 242 static inline void compaction_unregister_node(struct node *node)
 243 {
 244 }
 245 #endif /* CONFIG_COMPACTION && CONFIG_SYSFS && CONFIG_NUMA */
 246
 247 #endif /* _LINUX_COMPACTION_H */