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         /* 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 successful to compact
  39          * suitable pages.
  40          */
  41         COMPACT_COMPLETE,
  42         /*
  43          * direct compaction has scanned part of the zone but wasn't successful
  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 /*
  61  * Number of free order-0 pages that should be available above given watermark
  62  * to make sure compaction has reasonable chance of not running out of free
  63  * pages that it needs to isolate as migration target during its work.
  64  */
  65 static inline unsigned long compact_gap(unsigned int order)
  66 {
  67         /*
  68          * Although all the isolations for migration are temporary, compaction
  69          * free scanner may have up to 1 << order pages on its list and then
  70          * try to split an (order - 1) free page. At that point, a gap of
  71          * 1 << order might not be enough, so it's safer to require twice that
  72          * amount. Note that the number of pages on the list is also
  73          * effectively limited by COMPACT_CLUSTER_MAX, as that's the maximum
  74          * that the migrate scanner can have isolated on migrate list, and free
  75          * scanner is only invoked when the number of isolated free pages is
  76          * lower than that. But it's not worth to complicate the formula here
  77          * as a bigger gap for higher orders than strictly necessary can also
  78          * improve chances of compaction success.
  79          */
  80         return 2UL << order;
  81 }
  82
  83 #ifdef CONFIG_COMPACTION
  84 extern unsigned int sysctl_compaction_proactiveness;
  85 extern int sysctl_compaction_handler(struct ctl_table *table, int write,
  86                         void *buffer, size_t *length, loff_t *ppos);
  87 extern int compaction_proactiveness_sysctl_handler(struct ctl_table *table,
  88                 int write, void *buffer, size_t *length, loff_t *ppos);
  89 extern int sysctl_extfrag_threshold;
  90 extern int sysctl_compact_unevictable_allowed;
  91
  92 extern unsigned int extfrag_for_order(struct zone *zone, unsigned int order);
  93 extern int fragmentation_index(struct zone *zone, unsigned int order);
  94 extern enum compact_result try_to_compact_pages(gfp_t gfp_mask,
  95                 unsigned int order, unsigned int alloc_flags,
  96                 const struct alloc_context *ac, enum compact_priority prio,
  97                 struct page **page);
  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 highest_zoneidx);
 101
 102 extern void compaction_defer_reset(struct zone *zone, int order,
 103                                 bool alloc_success);
 104
 105 /* Compaction has made some progress and retrying makes sense */
 106 static inline bool compaction_made_progress(enum compact_result result)
 107 {
 108         /*
 109          * Even though this might sound confusing this in fact tells us
 110          * that the compaction successfully isolated and migrated some
 111          * pageblocks.
 112          */
 113         if (result == COMPACT_SUCCESS)
 114                 return true;
 115
 116         return false;
 117 }
 118
 119 /* Compaction has failed and it doesn't make much sense to keep retrying. */
 120 static inline bool compaction_failed(enum compact_result result)
 121 {
 122         /* All zones were scanned completely and still not result. */
 123         if (result == COMPACT_COMPLETE)
 124                 return true;
 125
 126         return false;
 127 }
 128
 129 /* Compaction needs reclaim to be performed first, so it can continue. */
 130 static inline bool compaction_needs_reclaim(enum compact_result result)
 131 {
 132         /*
 133          * Compaction backed off due to watermark checks for order-0
 134          * so the regular reclaim has to try harder and reclaim something.
 135          */
 136         if (result == COMPACT_SKIPPED)
 137                 return true;
 138
 139         return false;
 140 }
 141
 142 /*
 143  * Compaction has backed off for some reason after doing some work or none
 144  * at all. It might be throttling or lock contention. Retrying might be still
 145  * worthwhile, but with a higher priority if allowed.
 146  */
 147 static inline bool compaction_withdrawn(enum compact_result result)
 148 {
 149         /*
 150          * If compaction is deferred for high-order allocations, it is
 151          * because sync compaction recently failed. If this is the case
 152          * and the caller requested a THP allocation, we do not want
 153          * to heavily disrupt the system, so we fail the allocation
 154          * instead of entering direct reclaim.
 155          */
 156         if (result == COMPACT_DEFERRED)
 157                 return true;
 158
 159         /*
 160          * If compaction in async mode encounters contention or blocks higher
 161          * priority task we back off early rather than cause stalls.
 162          */
 163         if (result == COMPACT_CONTENDED)
 164                 return true;
 165
 166         /*
 167          * Page scanners have met but we haven't scanned full zones so this
 168          * is a back off in fact.
 169          */
 170         if (result == COMPACT_PARTIAL_SKIPPED)
 171                 return true;
 172
 173         return false;
 174 }
 175
 176
 177 bool compaction_zonelist_suitable(struct alloc_context *ac, int order,
 178                                         int alloc_flags);
 179
 180 extern int kcompactd_run(int nid);
 181 extern void kcompactd_stop(int nid);
 182 extern void wakeup_kcompactd(pg_data_t *pgdat, int order, int highest_zoneidx);
 183
 184 #else
 185 static inline void reset_isolation_suitable(pg_data_t *pgdat)
 186 {
 187 }
 188
 189 static inline enum compact_result compaction_suitable(struct zone *zone, int order,
 190                                         int alloc_flags, int highest_zoneidx)
 191 {
 192         return COMPACT_SKIPPED;
 193 }
 194
 195 static inline bool compaction_made_progress(enum compact_result result)
 196 {
 197         return false;
 198 }
 199
 200 static inline bool compaction_failed(enum compact_result result)
 201 {
 202         return false;
 203 }
 204
 205 static inline bool compaction_needs_reclaim(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,
 224                                 int order, int highest_zoneidx)
 225 {
 226 }
 227
 228 #endif /* CONFIG_COMPACTION */
 229
 230 struct node;
 231 #if defined(CONFIG_COMPACTION) && defined(CONFIG_SYSFS) && defined(CONFIG_NUMA)
 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 */