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 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 /*
  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 sysctl_extfrag_threshold;
  88 extern int sysctl_compact_unevictable_allowed;
  89
  90 extern unsigned int extfrag_for_order(struct zone *zone, unsigned int order);
  91 extern int fragmentation_index(struct zone *zone, unsigned int order);
  92 extern enum compact_result try_to_compact_pages(gfp_t gfp_mask,
  93                 unsigned int order, unsigned int alloc_flags,
  94                 const struct alloc_context *ac, enum compact_priority prio,
  95                 struct page **page);
  96 extern void reset_isolation_suitable(pg_data_t *pgdat);
  97 extern enum compact_result compaction_suitable(struct zone *zone, int order,
  98                 unsigned int alloc_flags, int highest_zoneidx);
  99
 100 extern void compaction_defer_reset(struct zone *zone, int order,
 101                                 bool alloc_success);
 102
 103 /* Compaction has made some progress and retrying makes sense */
 104 static inline bool compaction_made_progress(enum compact_result result)
 105 {
 106         /*
 107          * Even though this might sound confusing this in fact tells us
 108          * that the compaction successfully isolated and migrated some
 109          * pageblocks.
 110          */
 111         if (result == COMPACT_SUCCESS)
 112                 return true;
 113
 114         return false;
 115 }
 116
 117 /* Compaction has failed and it doesn't make much sense to keep retrying. */
 118 static inline bool compaction_failed(enum compact_result result)
 119 {
 120         /* All zones were scanned completely and still not result. */
 121         if (result == COMPACT_COMPLETE)
 122                 return true;
 123
 124         return false;
 125 }
 126
 127 /* Compaction needs reclaim to be performed first, so it can continue. */
 128 static inline bool compaction_needs_reclaim(enum compact_result result)
 129 {
 130         /*
 131          * Compaction backed off due to watermark checks for order-0
 132          * so the regular reclaim has to try harder and reclaim something.
 133          */
 134         if (result == COMPACT_SKIPPED)
 135                 return true;
 136
 137         return false;
 138 }
 139
 140 /*
 141  * Compaction has backed off for some reason after doing some work or none
 142  * at all. It might be throttling or lock contention. Retrying might be still
 143  * worthwhile, but with a higher priority if allowed.
 144  */
 145 static inline bool compaction_withdrawn(enum compact_result result)
 146 {
 147         /*
 148          * If compaction is deferred for high-order allocations, it is
 149          * because sync compaction recently failed. If this is the case
 150          * and the caller requested a THP allocation, we do not want
 151          * to heavily disrupt the system, so we fail the allocation
 152          * instead of entering direct reclaim.
 153          */
 154         if (result == COMPACT_DEFERRED)
 155                 return true;
 156
 157         /*
 158          * If compaction in async mode encounters contention or blocks higher
 159          * priority task we back off early rather than cause stalls.
 160          */
 161         if (result == COMPACT_CONTENDED)
 162                 return true;
 163
 164         /*
 165          * Page scanners have met but we haven't scanned full zones so this
 166          * is a back off in fact.
 167          */
 168         if (result == COMPACT_PARTIAL_SKIPPED)
 169                 return true;
 170
 171         return false;
 172 }
 173
 174
 175 bool compaction_zonelist_suitable(struct alloc_context *ac, int order,
 176                                         int alloc_flags);
 177
 178 extern int kcompactd_run(int nid);
 179 extern void kcompactd_stop(int nid);
 180 extern void wakeup_kcompactd(pg_data_t *pgdat, int order, int highest_zoneidx);
 181
 182 #else
 183 static inline void reset_isolation_suitable(pg_data_t *pgdat)
 184 {
 185 }
 186
 187 static inline enum compact_result compaction_suitable(struct zone *zone, int order,
 188                                         int alloc_flags, int highest_zoneidx)
 189 {
 190         return COMPACT_SKIPPED;
 191 }
 192
 193 static inline bool compaction_made_progress(enum compact_result result)
 194 {
 195         return false;
 196 }
 197
 198 static inline bool compaction_failed(enum compact_result result)
 199 {
 200         return false;
 201 }
 202
 203 static inline bool compaction_needs_reclaim(enum compact_result result)
 204 {
 205         return false;
 206 }
 207
 208 static inline bool compaction_withdrawn(enum compact_result result)
 209 {
 210         return true;
 211 }
 212
 213 static inline int kcompactd_run(int nid)
 214 {
 215         return 0;
 216 }
 217 static inline void kcompactd_stop(int nid)
 218 {
 219 }
 220
 221 static inline void wakeup_kcompactd(pg_data_t *pgdat,
 222                                 int order, int highest_zoneidx)
 223 {
 224 }
 225
 226 #endif /* CONFIG_COMPACTION */
 227
 228 struct node;
 229 #if defined(CONFIG_COMPACTION) && defined(CONFIG_SYSFS) && defined(CONFIG_NUMA)
 230 extern int compaction_register_node(struct node *node);
 231 extern void compaction_unregister_node(struct node *node);
 232
 233 #else
 234
 235 static inline int compaction_register_node(struct node *node)
 236 {
 237         return 0;
 238 }
 239
 240 static inline void compaction_unregister_node(struct node *node)
 241 {
 242 }
 243 #endif /* CONFIG_COMPACTION && CONFIG_SYSFS && CONFIG_NUMA */
 244
 245 #endif /* _LINUX_COMPACTION_H */