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 void 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 void kcompactd_run(int nid) 216 { 217 } 218 static inline void kcompactd_stop(int nid) 219 { 220 } 221 222 static inline void wakeup_kcompactd(pg_data_t *pgdat, 223 int order, int highest_zoneidx) 224 { 225 } 226 227 #endif /* CONFIG_COMPACTION */ 228 229 struct node; 230 #if defined(CONFIG_COMPACTION) && defined(CONFIG_SYSFS) && defined(CONFIG_NUMA) 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 */ 247