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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 successful to compact
39 : * suitable pages.
40 : */
41 : COMPACT_COMPLETE,
42 : /*
43 : * direct compaction has scanned part of the zone but wasn't successful
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 0 : return 2UL << order;
81 : }
82 :
83 : #ifdef CONFIG_COMPACTION
84 :
85 : extern unsigned int extfrag_for_order(struct zone *zone, unsigned int order);
86 : extern int fragmentation_index(struct zone *zone, unsigned int order);
87 : extern enum compact_result try_to_compact_pages(gfp_t gfp_mask,
88 : unsigned int order, unsigned int alloc_flags,
89 : const struct alloc_context *ac, enum compact_priority prio,
90 : struct page **page);
91 : extern void reset_isolation_suitable(pg_data_t *pgdat);
92 : extern enum compact_result compaction_suitable(struct zone *zone, int order,
93 : unsigned int alloc_flags, int highest_zoneidx);
94 :
95 : extern void compaction_defer_reset(struct zone *zone, int order,
96 : bool alloc_success);
97 :
98 : /* Compaction has made some progress and retrying makes sense */
99 : static inline bool compaction_made_progress(enum compact_result result)
100 : {
101 : /*
102 : * Even though this might sound confusing this in fact tells us
103 : * that the compaction successfully isolated and migrated some
104 : * pageblocks.
105 : */
106 0 : if (result == COMPACT_SUCCESS)
107 : return true;
108 :
109 : return false;
110 : }
111 :
112 : /* Compaction has failed and it doesn't make much sense to keep retrying. */
113 : static inline bool compaction_failed(enum compact_result result)
114 : {
115 : /* All zones were scanned completely and still not result. */
116 0 : if (result == COMPACT_COMPLETE)
117 : return true;
118 :
119 : return false;
120 : }
121 :
122 : /* Compaction needs reclaim to be performed first, so it can continue. */
123 : static inline bool compaction_needs_reclaim(enum compact_result result)
124 : {
125 : /*
126 : * Compaction backed off due to watermark checks for order-0
127 : * so the regular reclaim has to try harder and reclaim something.
128 : */
129 0 : if (result == COMPACT_SKIPPED)
130 : return true;
131 :
132 : return false;
133 : }
134 :
135 : /*
136 : * Compaction has backed off for some reason after doing some work or none
137 : * at all. It might be throttling or lock contention. Retrying might be still
138 : * worthwhile, but with a higher priority if allowed.
139 : */
140 : static inline bool compaction_withdrawn(enum compact_result result)
141 : {
142 : /*
143 : * If compaction is deferred for high-order allocations, it is
144 : * because sync compaction recently failed. If this is the case
145 : * and the caller requested a THP allocation, we do not want
146 : * to heavily disrupt the system, so we fail the allocation
147 : * instead of entering direct reclaim.
148 : */
149 0 : if (result == COMPACT_DEFERRED)
150 : return true;
151 :
152 : /*
153 : * If compaction in async mode encounters contention or blocks higher
154 : * priority task we back off early rather than cause stalls.
155 : */
156 0 : if (result == COMPACT_CONTENDED)
157 : return true;
158 :
159 : /*
160 : * Page scanners have met but we haven't scanned full zones so this
161 : * is a back off in fact.
162 : */
163 0 : if (result == COMPACT_PARTIAL_SKIPPED)
164 : return true;
165 :
166 : return false;
167 : }
168 :
169 :
170 : bool compaction_zonelist_suitable(struct alloc_context *ac, int order,
171 : int alloc_flags);
172 :
173 : extern void kcompactd_run(int nid);
174 : extern void kcompactd_stop(int nid);
175 : extern void wakeup_kcompactd(pg_data_t *pgdat, int order, int highest_zoneidx);
176 :
177 : #else
178 : static inline void reset_isolation_suitable(pg_data_t *pgdat)
179 : {
180 : }
181 :
182 : static inline enum compact_result compaction_suitable(struct zone *zone, int order,
183 : int alloc_flags, int highest_zoneidx)
184 : {
185 : return COMPACT_SKIPPED;
186 : }
187 :
188 : static inline bool compaction_made_progress(enum compact_result result)
189 : {
190 : return false;
191 : }
192 :
193 : static inline bool compaction_failed(enum compact_result result)
194 : {
195 : return false;
196 : }
197 :
198 : static inline bool compaction_needs_reclaim(enum compact_result result)
199 : {
200 : return false;
201 : }
202 :
203 : static inline bool compaction_withdrawn(enum compact_result result)
204 : {
205 : return true;
206 : }
207 :
208 : static inline void kcompactd_run(int nid)
209 : {
210 : }
211 : static inline void kcompactd_stop(int nid)
212 : {
213 : }
214 :
215 : static inline void wakeup_kcompactd(pg_data_t *pgdat,
216 : int order, int highest_zoneidx)
217 : {
218 : }
219 :
220 : #endif /* CONFIG_COMPACTION */
221 :
222 : struct node;
223 : #if defined(CONFIG_COMPACTION) && defined(CONFIG_SYSFS) && defined(CONFIG_NUMA)
224 : extern int compaction_register_node(struct node *node);
225 : extern void compaction_unregister_node(struct node *node);
226 :
227 : #else
228 :
229 : static inline int compaction_register_node(struct node *node)
230 : {
231 : return 0;
232 : }
233 :
234 : static inline void compaction_unregister_node(struct node *node)
235 : {
236 : }
237 : #endif /* CONFIG_COMPACTION && CONFIG_SYSFS && CONFIG_NUMA */
238 :
239 : #endif /* _LINUX_COMPACTION_H */
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