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 85 extern unsigned int extfrag_for_order(struct zone *zone, unsigned int order); 86 extern int fragmentation_index(struct zone *zone, unsigned int order); 87 extern enum compact_result try_to_compact_pages(gfp_t gfp_mask, 88 unsigned int order, unsigned int alloc_flags, 89 const struct alloc_context *ac, enum compact_priority prio, 90 struct page **page); 91 extern void reset_isolation_suitable(pg_data_t *pgdat); 92 extern enum compact_result compaction_suitable(struct zone *zone, int order, 93 unsigned int alloc_flags, int highest_zoneidx); 94 95 extern void compaction_defer_reset(struct zone *zone, int order, 96 bool alloc_success); 97 98 /* Compaction has made some progress and retrying makes sense */ 99 static inline bool compaction_made_progress(enum compact_result result) 100 { 101 /* 102 * Even though this might sound confusing this in fact tells us 103 * that the compaction successfully isolated and migrated some 104 * pageblocks. 105 */ 106 if (result == COMPACT_SUCCESS) 107 return true; 108 109 return false; 110 } 111 112 /* Compaction has failed and it doesn't make much sense to keep retrying. */ 113 static inline bool compaction_failed(enum compact_result result) 114 { 115 /* All zones were scanned completely and still not result. */ 116 if (result == COMPACT_COMPLETE) 117 return true; 118 119 return false; 120 } 121 122 /* Compaction needs reclaim to be performed first, so it can continue. */ 123 static inline bool compaction_needs_reclaim(enum compact_result result) 124 { 125 /* 126 * Compaction backed off due to watermark checks for order-0 127 * so the regular reclaim has to try harder and reclaim something. 128 */ 129 if (result == COMPACT_SKIPPED) 130 return true; 131 132 return false; 133 } 134 135 /* 136 * Compaction has backed off for some reason after doing some work or none 137 * at all. It might be throttling or lock contention. Retrying might be still 138 * worthwhile, but with a higher priority if allowed. 139 */ 140 static inline bool compaction_withdrawn(enum compact_result result) 141 { 142 /* 143 * If compaction is deferred for high-order allocations, it is 144 * because sync compaction recently failed. If this is the case 145 * and the caller requested a THP allocation, we do not want 146 * to heavily disrupt the system, so we fail the allocation 147 * instead of entering direct reclaim. 148 */ 149 if (result == COMPACT_DEFERRED) 150 return true; 151 152 /* 153 * If compaction in async mode encounters contention or blocks higher 154 * priority task we back off early rather than cause stalls. 155 */ 156 if (result == COMPACT_CONTENDED) 157 return true; 158 159 /* 160 * Page scanners have met but we haven't scanned full zones so this 161 * is a back off in fact. 162 */ 163 if (result == COMPACT_PARTIAL_SKIPPED) 164 return true; 165 166 return false; 167 } 168 169 170 bool compaction_zonelist_suitable(struct alloc_context *ac, int order, 171 int alloc_flags); 172 173 extern void kcompactd_run(int nid); 174 extern void kcompactd_stop(int nid); 175 extern void wakeup_kcompactd(pg_data_t *pgdat, int order, int highest_zoneidx); 176 177 #else 178 static inline void reset_isolation_suitable(pg_data_t *pgdat) 179 { 180 } 181 182 static inline enum compact_result compaction_suitable(struct zone *zone, int order, 183 int alloc_flags, int highest_zoneidx) 184 { 185 return COMPACT_SKIPPED; 186 } 187 188 static inline bool compaction_made_progress(enum compact_result result) 189 { 190 return false; 191 } 192 193 static inline bool compaction_failed(enum compact_result result) 194 { 195 return false; 196 } 197 198 static inline bool compaction_needs_reclaim(enum compact_result result) 199 { 200 return false; 201 } 202 203 static inline bool compaction_withdrawn(enum compact_result result) 204 { 205 return true; 206 } 207 208 static inline void kcompactd_run(int nid) 209 { 210 } 211 static inline void kcompactd_stop(int nid) 212 { 213 } 214 215 static inline void wakeup_kcompactd(pg_data_t *pgdat, 216 int order, int highest_zoneidx) 217 { 218 } 219 220 #endif /* CONFIG_COMPACTION */ 221 222 struct node; 223 #if defined(CONFIG_COMPACTION) && defined(CONFIG_SYSFS) && defined(CONFIG_NUMA) 224 extern int compaction_register_node(struct node *node); 225 extern void compaction_unregister_node(struct node *node); 226 227 #else 228 229 static inline int compaction_register_node(struct node *node) 230 { 231 return 0; 232 } 233 234 static inline void compaction_unregister_node(struct node *node) 235 { 236 } 237 #endif /* CONFIG_COMPACTION && CONFIG_SYSFS && CONFIG_NUMA */ 238 239 #endif /* _LINUX_COMPACTION_H */ 240