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 /* compaction not active last round */ 33 COMPACT_INACTIVE = COMPACT_DEFERRED, 34 35 /* For more detailed tracepoint output - internal to compaction */ 36 COMPACT_NO_SUITABLE_PAGE, 37 /* compaction should continue to another pageblock */ 38 COMPACT_CONTINUE, 39 40 /* 41 * The full zone was compacted scanned but wasn't successfull to compact 42 * suitable pages. 43 */ 44 COMPACT_COMPLETE, 45 /* 46 * direct compaction has scanned part of the zone but wasn't successfull 47 * to compact suitable pages. 48 */ 49 COMPACT_PARTIAL_SKIPPED, 50 51 /* compaction terminated prematurely due to lock contentions */ 52 COMPACT_CONTENDED, 53 54 /* 55 * direct compaction terminated after concluding that the allocation 56 * should now succeed 57 */ 58 COMPACT_SUCCESS, 59 }; 60 61 struct alloc_context; /* in mm/internal.h */ 62 63 /* 64 * Number of free order-0 pages that should be available above given watermark 65 * to make sure compaction has reasonable chance of not running out of free 66 * pages that it needs to isolate as migration target during its work. 67 */ 68 static inline unsigned long compact_gap(unsigned int order) 69 { 70 /* 71 * Although all the isolations for migration are temporary, compaction 72 * free scanner may have up to 1 << order pages on its list and then 73 * try to split an (order - 1) free page. At that point, a gap of 74 * 1 << order might not be enough, so it's safer to require twice that 75 * amount. Note that the number of pages on the list is also 76 * effectively limited by COMPACT_CLUSTER_MAX, as that's the maximum 77 * that the migrate scanner can have isolated on migrate list, and free 78 * scanner is only invoked when the number of isolated free pages is 79 * lower than that. But it's not worth to complicate the formula here 80 * as a bigger gap for higher orders than strictly necessary can also 81 * improve chances of compaction success. 82 */ 83 return 2UL << order; 84 } 85 86 #ifdef CONFIG_COMPACTION 87 extern int sysctl_compact_memory; 88 extern int sysctl_compaction_handler(struct ctl_table *table, int write, 89 void __user *buffer, size_t *length, loff_t *ppos); 90 extern int sysctl_extfrag_threshold; 91 extern int sysctl_extfrag_handler(struct ctl_table *table, int write, 92 void __user *buffer, size_t *length, loff_t *ppos); 93 extern int sysctl_compact_unevictable_allowed; 94 95 extern int fragmentation_index(struct zone *zone, unsigned int order); 96 extern enum compact_result try_to_compact_pages(gfp_t gfp_mask, 97 unsigned int order, unsigned int alloc_flags, 98 const struct alloc_context *ac, enum compact_priority prio); 99 extern void reset_isolation_suitable(pg_data_t *pgdat); 100 extern enum compact_result compaction_suitable(struct zone *zone, int order, 101 unsigned int alloc_flags, int classzone_idx); 102 103 extern void defer_compaction(struct zone *zone, int order); 104 extern bool compaction_deferred(struct zone *zone, int order); 105 extern void compaction_defer_reset(struct zone *zone, int order, 106 bool alloc_success); 107 extern bool compaction_restarting(struct zone *zone, int order); 108 109 /* Compaction has made some progress and retrying makes sense */ 110 static inline bool compaction_made_progress(enum compact_result result) 111 { 112 /* 113 * Even though this might sound confusing this in fact tells us 114 * that the compaction successfully isolated and migrated some 115 * pageblocks. 116 */ 117 if (result == COMPACT_SUCCESS) 118 return true; 119 120 return false; 121 } 122 123 /* Compaction has failed and it doesn't make much sense to keep retrying. */ 124 static inline bool compaction_failed(enum compact_result result) 125 { 126 /* All zones were scanned completely and still not result. */ 127 if (result == COMPACT_COMPLETE) 128 return true; 129 130 return false; 131 } 132 133 /* 134 * Compaction has backed off for some reason. It might be throttling or 135 * lock contention. Retrying is still worthwhile. 136 */ 137 static inline bool compaction_withdrawn(enum compact_result result) 138 { 139 /* 140 * Compaction backed off due to watermark checks for order-0 141 * so the regular reclaim has to try harder and reclaim something. 142 */ 143 if (result == COMPACT_SKIPPED) 144 return true; 145 146 /* 147 * If compaction is deferred for high-order allocations, it is 148 * because sync compaction recently failed. If this is the case 149 * and the caller requested a THP allocation, we do not want 150 * to heavily disrupt the system, so we fail the allocation 151 * instead of entering direct reclaim. 152 */ 153 if (result == COMPACT_DEFERRED) 154 return true; 155 156 /* 157 * If compaction in async mode encounters contention or blocks higher 158 * priority task we back off early rather than cause stalls. 159 */ 160 if (result == COMPACT_CONTENDED) 161 return true; 162 163 /* 164 * Page scanners have met but we haven't scanned full zones so this 165 * is a back off in fact. 166 */ 167 if (result == COMPACT_PARTIAL_SKIPPED) 168 return true; 169 170 return false; 171 } 172 173 174 bool compaction_zonelist_suitable(struct alloc_context *ac, int order, 175 int alloc_flags); 176 177 extern int kcompactd_run(int nid); 178 extern void kcompactd_stop(int nid); 179 extern void wakeup_kcompactd(pg_data_t *pgdat, int order, int classzone_idx); 180 181 #else 182 static inline void reset_isolation_suitable(pg_data_t *pgdat) 183 { 184 } 185 186 static inline enum compact_result compaction_suitable(struct zone *zone, int order, 187 int alloc_flags, int classzone_idx) 188 { 189 return COMPACT_SKIPPED; 190 } 191 192 static inline void defer_compaction(struct zone *zone, int order) 193 { 194 } 195 196 static inline bool compaction_deferred(struct zone *zone, int order) 197 { 198 return true; 199 } 200 201 static inline bool compaction_made_progress(enum compact_result result) 202 { 203 return false; 204 } 205 206 static inline bool compaction_failed(enum compact_result result) 207 { 208 return false; 209 } 210 211 static inline bool compaction_withdrawn(enum compact_result result) 212 { 213 return true; 214 } 215 216 static inline int kcompactd_run(int nid) 217 { 218 return 0; 219 } 220 static inline void kcompactd_stop(int nid) 221 { 222 } 223 224 static inline void wakeup_kcompactd(pg_data_t *pgdat, int order, int classzone_idx) 225 { 226 } 227 228 #endif /* CONFIG_COMPACTION */ 229 230 #if defined(CONFIG_COMPACTION) && defined(CONFIG_SYSFS) && defined(CONFIG_NUMA) 231 struct node; 232 extern int compaction_register_node(struct node *node); 233 extern void compaction_unregister_node(struct node *node); 234 235 #else 236 237 static inline int compaction_register_node(struct node *node) 238 { 239 return 0; 240 } 241 242 static inline void compaction_unregister_node(struct node *node) 243 { 244 } 245 #endif /* CONFIG_COMPACTION && CONFIG_SYSFS && CONFIG_NUMA */ 246 247 #endif /* _LINUX_COMPACTION_H */ 248