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 */
compact_gap(unsigned int order)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 compaction_proactiveness_sysctl_handler(struct ctl_table *table,
89 int write, void *buffer, size_t *length, loff_t *ppos);
90 extern int sysctl_extfrag_threshold;
91 extern int sysctl_compact_unevictable_allowed;
92
93 extern unsigned int extfrag_for_order(struct zone *zone, unsigned int order);
94 extern int fragmentation_index(struct zone *zone, unsigned int order);
95 extern enum compact_result try_to_compact_pages(gfp_t gfp_mask,
96 unsigned int order, unsigned int alloc_flags,
97 const struct alloc_context *ac, enum compact_priority prio,
98 struct page **page);
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 highest_zoneidx);
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 */
compaction_made_progress(enum compact_result result)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. */
compaction_failed(enum compact_result result)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 /* Compaction needs reclaim to be performed first, so it can continue. */
compaction_needs_reclaim(enum compact_result result)134 static inline bool compaction_needs_reclaim(enum compact_result result)
135 {
136 /*
137 * Compaction backed off due to watermark checks for order-0
138 * so the regular reclaim has to try harder and reclaim something.
139 */
140 if (result == COMPACT_SKIPPED)
141 return true;
142
143 return false;
144 }
145
146 /*
147 * Compaction has backed off for some reason after doing some work or none
148 * at all. It might be throttling or lock contention. Retrying might be still
149 * worthwhile, but with a higher priority if allowed.
150 */
compaction_withdrawn(enum compact_result result)151 static inline bool compaction_withdrawn(enum compact_result result)
152 {
153 /*
154 * If compaction is deferred for high-order allocations, it is
155 * because sync compaction recently failed. If this is the case
156 * and the caller requested a THP allocation, we do not want
157 * to heavily disrupt the system, so we fail the allocation
158 * instead of entering direct reclaim.
159 */
160 if (result == COMPACT_DEFERRED)
161 return true;
162
163 /*
164 * If compaction in async mode encounters contention or blocks higher
165 * priority task we back off early rather than cause stalls.
166 */
167 if (result == COMPACT_CONTENDED)
168 return true;
169
170 /*
171 * Page scanners have met but we haven't scanned full zones so this
172 * is a back off in fact.
173 */
174 if (result == COMPACT_PARTIAL_SKIPPED)
175 return true;
176
177 return false;
178 }
179
180
181 bool compaction_zonelist_suitable(struct alloc_context *ac, int order,
182 int alloc_flags);
183
184 extern int kcompactd_run(int nid);
185 extern void kcompactd_stop(int nid);
186 extern void wakeup_kcompactd(pg_data_t *pgdat, int order, int highest_zoneidx);
187 extern unsigned long isolate_and_split_free_page(struct page *page,
188 struct list_head *list);
189
190 #else
reset_isolation_suitable(pg_data_t * pgdat)191 static inline void reset_isolation_suitable(pg_data_t *pgdat)
192 {
193 }
194
compaction_suitable(struct zone * zone,int order,int alloc_flags,int highest_zoneidx)195 static inline enum compact_result compaction_suitable(struct zone *zone, int order,
196 int alloc_flags, int highest_zoneidx)
197 {
198 return COMPACT_SKIPPED;
199 }
200
defer_compaction(struct zone * zone,int order)201 static inline void defer_compaction(struct zone *zone, int order)
202 {
203 }
204
compaction_deferred(struct zone * zone,int order)205 static inline bool compaction_deferred(struct zone *zone, int order)
206 {
207 return true;
208 }
209
compaction_made_progress(enum compact_result result)210 static inline bool compaction_made_progress(enum compact_result result)
211 {
212 return false;
213 }
214
compaction_failed(enum compact_result result)215 static inline bool compaction_failed(enum compact_result result)
216 {
217 return false;
218 }
219
compaction_needs_reclaim(enum compact_result result)220 static inline bool compaction_needs_reclaim(enum compact_result result)
221 {
222 return false;
223 }
224
compaction_withdrawn(enum compact_result result)225 static inline bool compaction_withdrawn(enum compact_result result)
226 {
227 return true;
228 }
229
kcompactd_run(int nid)230 static inline int kcompactd_run(int nid)
231 {
232 return 0;
233 }
kcompactd_stop(int nid)234 static inline void kcompactd_stop(int nid)
235 {
236 }
237
wakeup_kcompactd(pg_data_t * pgdat,int order,int highest_zoneidx)238 static inline void wakeup_kcompactd(pg_data_t *pgdat,
239 int order, int highest_zoneidx)
240 {
241 }
242
isolate_and_split_free_page(struct page * page,struct list_head * list)243 static inline unsigned long isolate_and_split_free_page(struct page *page,
244 struct list_head *list)
245 {
246 return 0;
247 }
248
249 #endif /* CONFIG_COMPACTION */
250
251 struct node;
252 #if defined(CONFIG_COMPACTION) && defined(CONFIG_SYSFS) && defined(CONFIG_NUMA)
253 extern int compaction_register_node(struct node *node);
254 extern void compaction_unregister_node(struct node *node);
255
256 #else
257
compaction_register_node(struct node * node)258 static inline int compaction_register_node(struct node *node)
259 {
260 return 0;
261 }
262
compaction_unregister_node(struct node * node)263 static inline void compaction_unregister_node(struct node *node)
264 {
265 }
266 #endif /* CONFIG_COMPACTION && CONFIG_SYSFS && CONFIG_NUMA */
267
268 #endif /* _LINUX_COMPACTION_H */
269