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