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 int sysctl_compact_memory; 85 extern unsigned int sysctl_compaction_proactiveness; 86 extern int sysctl_compaction_handler(struct ctl_table *table, int write, 87 void *buffer, size_t *length, loff_t *ppos); 88 extern int sysctl_extfrag_threshold; 89 extern int sysctl_compact_unevictable_allowed; 90 91 extern unsigned int extfrag_for_order(struct zone *zone, unsigned int order); 92 extern int fragmentation_index(struct zone *zone, unsigned int order); 93 extern enum compact_result try_to_compact_pages(gfp_t gfp_mask, 94 unsigned int order, unsigned int alloc_flags, 95 const struct alloc_context *ac, enum compact_priority prio, 96 struct page **page); 97 extern void reset_isolation_suitable(pg_data_t *pgdat); 98 extern enum compact_result compaction_suitable(struct zone *zone, int order, 99 unsigned int alloc_flags, int highest_zoneidx); 100 101 extern void defer_compaction(struct zone *zone, int order); 102 extern bool compaction_deferred(struct zone *zone, int order); 103 extern void compaction_defer_reset(struct zone *zone, int order, 104 bool alloc_success); 105 extern bool compaction_restarting(struct zone *zone, int order); 106 107 /* Compaction has made some progress and retrying makes sense */ 108 static inline bool compaction_made_progress(enum compact_result result) 109 { 110 /* 111 * Even though this might sound confusing this in fact tells us 112 * that the compaction successfully isolated and migrated some 113 * pageblocks. 114 */ 115 if (result == COMPACT_SUCCESS) 116 return true; 117 118 return false; 119 } 120 121 /* Compaction has failed and it doesn't make much sense to keep retrying. */ 122 static inline bool compaction_failed(enum compact_result result) 123 { 124 /* All zones were scanned completely and still not result. */ 125 if (result == COMPACT_COMPLETE) 126 return true; 127 128 return false; 129 } 130 131 /* Compaction needs reclaim to be performed first, so it can continue. */ 132 static inline bool compaction_needs_reclaim(enum compact_result result) 133 { 134 /* 135 * Compaction backed off due to watermark checks for order-0 136 * so the regular reclaim has to try harder and reclaim something. 137 */ 138 if (result == COMPACT_SKIPPED) 139 return true; 140 141 return false; 142 } 143 144 /* 145 * Compaction has backed off for some reason after doing some work or none 146 * at all. It might be throttling or lock contention. Retrying might be still 147 * worthwhile, but with a higher priority if allowed. 148 */ 149 static inline bool compaction_withdrawn(enum compact_result result) 150 { 151 /* 152 * If compaction is deferred for high-order allocations, it is 153 * because sync compaction recently failed. If this is the case 154 * and the caller requested a THP allocation, we do not want 155 * to heavily disrupt the system, so we fail the allocation 156 * instead of entering direct reclaim. 157 */ 158 if (result == COMPACT_DEFERRED) 159 return true; 160 161 /* 162 * If compaction in async mode encounters contention or blocks higher 163 * priority task we back off early rather than cause stalls. 164 */ 165 if (result == COMPACT_CONTENDED) 166 return true; 167 168 /* 169 * Page scanners have met but we haven't scanned full zones so this 170 * is a back off in fact. 171 */ 172 if (result == COMPACT_PARTIAL_SKIPPED) 173 return true; 174 175 return false; 176 } 177 178 179 bool compaction_zonelist_suitable(struct alloc_context *ac, int order, 180 int alloc_flags); 181 182 extern int kcompactd_run(int nid); 183 extern void kcompactd_stop(int nid); 184 extern void wakeup_kcompactd(pg_data_t *pgdat, int order, int highest_zoneidx); 185 186 #else 187 static inline void reset_isolation_suitable(pg_data_t *pgdat) 188 { 189 } 190 191 static inline enum compact_result compaction_suitable(struct zone *zone, int order, 192 int alloc_flags, int highest_zoneidx) 193 { 194 return COMPACT_SKIPPED; 195 } 196 197 static inline void defer_compaction(struct zone *zone, int order) 198 { 199 } 200 201 static inline bool compaction_deferred(struct zone *zone, int order) 202 { 203 return true; 204 } 205 206 static inline bool compaction_made_progress(enum compact_result result) 207 { 208 return false; 209 } 210 211 static inline bool compaction_failed(enum compact_result result) 212 { 213 return false; 214 } 215 216 static inline bool compaction_needs_reclaim(enum compact_result result) 217 { 218 return false; 219 } 220 221 static inline bool compaction_withdrawn(enum compact_result result) 222 { 223 return true; 224 } 225 226 static inline int kcompactd_run(int nid) 227 { 228 return 0; 229 } 230 static inline void kcompactd_stop(int nid) 231 { 232 } 233 234 static inline void wakeup_kcompactd(pg_data_t *pgdat, 235 int order, int highest_zoneidx) 236 { 237 } 238 239 #endif /* CONFIG_COMPACTION */ 240 241 struct node; 242 #if defined(CONFIG_COMPACTION) && defined(CONFIG_SYSFS) && defined(CONFIG_NUMA) 243 extern int compaction_register_node(struct node *node); 244 extern void compaction_unregister_node(struct node *node); 245 246 #else 247 248 static inline int compaction_register_node(struct node *node) 249 { 250 return 0; 251 } 252 253 static inline void compaction_unregister_node(struct node *node) 254 { 255 } 256 #endif /* CONFIG_COMPACTION && CONFIG_SYSFS && CONFIG_NUMA */ 257 258 #endif /* _LINUX_COMPACTION_H */ 259