1 #ifndef _LINUX_COMPACTION_H 2 #define _LINUX_COMPACTION_H 3 4 /* 5 * Determines how hard direct compaction should try to succeed. 6 * Lower value means higher priority, analogically to reclaim priority. 7 */ 8 enum compact_priority { 9 COMPACT_PRIO_SYNC_FULL, 10 MIN_COMPACT_PRIORITY = COMPACT_PRIO_SYNC_FULL, 11 COMPACT_PRIO_SYNC_LIGHT, 12 DEF_COMPACT_PRIORITY = COMPACT_PRIO_SYNC_LIGHT, 13 COMPACT_PRIO_ASYNC, 14 INIT_COMPACT_PRIORITY = COMPACT_PRIO_ASYNC 15 }; 16 17 /* Return values for compact_zone() and try_to_compact_pages() */ 18 /* When adding new states, please adjust include/trace/events/compaction.h */ 19 enum compact_result { 20 /* For more detailed tracepoint output - internal to compaction */ 21 COMPACT_NOT_SUITABLE_ZONE, 22 /* 23 * compaction didn't start as it was not possible or direct reclaim 24 * was more suitable 25 */ 26 COMPACT_SKIPPED, 27 /* compaction didn't start as it was deferred due to past failures */ 28 COMPACT_DEFERRED, 29 30 /* compaction not active last round */ 31 COMPACT_INACTIVE = COMPACT_DEFERRED, 32 33 /* For more detailed tracepoint output - internal to compaction */ 34 COMPACT_NO_SUITABLE_PAGE, 35 /* compaction should continue to another pageblock */ 36 COMPACT_CONTINUE, 37 38 /* 39 * The full zone was compacted scanned but wasn't successfull to compact 40 * suitable pages. 41 */ 42 COMPACT_COMPLETE, 43 /* 44 * direct compaction has scanned part of the zone but wasn't successfull 45 * to compact suitable pages. 46 */ 47 COMPACT_PARTIAL_SKIPPED, 48 49 /* compaction terminated prematurely due to lock contentions */ 50 COMPACT_CONTENDED, 51 52 /* 53 * direct compaction terminated after concluding that the allocation 54 * should now succeed 55 */ 56 COMPACT_SUCCESS, 57 }; 58 59 struct alloc_context; /* in mm/internal.h */ 60 61 /* 62 * Number of free order-0 pages that should be available above given watermark 63 * to make sure compaction has reasonable chance of not running out of free 64 * pages that it needs to isolate as migration target during its work. 65 */ 66 static inline unsigned long compact_gap(unsigned int order) 67 { 68 /* 69 * Although all the isolations for migration are temporary, compaction 70 * free scanner may have up to 1 << order pages on its list and then 71 * try to split an (order - 1) free page. At that point, a gap of 72 * 1 << order might not be enough, so it's safer to require twice that 73 * amount. Note that the number of pages on the list is also 74 * effectively limited by COMPACT_CLUSTER_MAX, as that's the maximum 75 * that the migrate scanner can have isolated on migrate list, and free 76 * scanner is only invoked when the number of isolated free pages is 77 * lower than that. But it's not worth to complicate the formula here 78 * as a bigger gap for higher orders than strictly necessary can also 79 * improve chances of compaction success. 80 */ 81 return 2UL << order; 82 } 83 84 #ifdef CONFIG_COMPACTION 85 extern int sysctl_compact_memory; 86 extern int sysctl_compaction_handler(struct ctl_table *table, int write, 87 void __user *buffer, size_t *length, loff_t *ppos); 88 extern int sysctl_extfrag_threshold; 89 extern int sysctl_extfrag_handler(struct ctl_table *table, int write, 90 void __user *buffer, size_t *length, loff_t *ppos); 91 extern int sysctl_compact_unevictable_allowed; 92 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 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 classzone_idx); 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 /* 132 * Compaction has backed off for some reason. It might be throttling or 133 * lock contention. Retrying is still worthwhile. 134 */ 135 static inline bool compaction_withdrawn(enum compact_result result) 136 { 137 /* 138 * Compaction backed off due to watermark checks for order-0 139 * so the regular reclaim has to try harder and reclaim something. 140 */ 141 if (result == COMPACT_SKIPPED) 142 return true; 143 144 /* 145 * If compaction is deferred for high-order allocations, it is 146 * because sync compaction recently failed. If this is the case 147 * and the caller requested a THP allocation, we do not want 148 * to heavily disrupt the system, so we fail the allocation 149 * instead of entering direct reclaim. 150 */ 151 if (result == COMPACT_DEFERRED) 152 return true; 153 154 /* 155 * If compaction in async mode encounters contention or blocks higher 156 * priority task we back off early rather than cause stalls. 157 */ 158 if (result == COMPACT_CONTENDED) 159 return true; 160 161 /* 162 * Page scanners have met but we haven't scanned full zones so this 163 * is a back off in fact. 164 */ 165 if (result == COMPACT_PARTIAL_SKIPPED) 166 return true; 167 168 return false; 169 } 170 171 172 bool compaction_zonelist_suitable(struct alloc_context *ac, int order, 173 int alloc_flags); 174 175 extern int kcompactd_run(int nid); 176 extern void kcompactd_stop(int nid); 177 extern void wakeup_kcompactd(pg_data_t *pgdat, int order, int classzone_idx); 178 179 #else 180 static inline void reset_isolation_suitable(pg_data_t *pgdat) 181 { 182 } 183 184 static inline enum compact_result compaction_suitable(struct zone *zone, int order, 185 int alloc_flags, int classzone_idx) 186 { 187 return COMPACT_SKIPPED; 188 } 189 190 static inline void defer_compaction(struct zone *zone, int order) 191 { 192 } 193 194 static inline bool compaction_deferred(struct zone *zone, int order) 195 { 196 return true; 197 } 198 199 static inline bool compaction_made_progress(enum compact_result result) 200 { 201 return false; 202 } 203 204 static inline bool compaction_failed(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, int order, int classzone_idx) 223 { 224 } 225 226 #endif /* CONFIG_COMPACTION */ 227 228 #if defined(CONFIG_COMPACTION) && defined(CONFIG_SYSFS) && defined(CONFIG_NUMA) 229 struct node; 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