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 */ 246