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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 */
9enum 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 */
21enum 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
58struct 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 */
65static 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
84extern unsigned int sysctl_compaction_proactiveness;
85extern int sysctl_compaction_handler(struct ctl_table *table, int write,
86 void *buffer, size_t *length, loff_t *ppos);
87extern int sysctl_extfrag_threshold;
88extern int sysctl_compact_unevictable_allowed;
89
90extern unsigned int extfrag_for_order(struct zone *zone, unsigned int order);
91extern int fragmentation_index(struct zone *zone, unsigned int order);
92extern enum compact_result try_to_compact_pages(gfp_t gfp_mask,
93 unsigned int order, unsigned int alloc_flags,
94 const struct alloc_context *ac, enum compact_priority prio,
95 struct page **page);
96extern void reset_isolation_suitable(pg_data_t *pgdat);
97extern enum compact_result compaction_suitable(struct zone *zone, int order,
98 unsigned int alloc_flags, int highest_zoneidx);
99
100extern void compaction_defer_reset(struct zone *zone, int order,
101 bool alloc_success);
102
103/* Compaction has made some progress and retrying makes sense */
104static inline bool compaction_made_progress(enum compact_result result)
105{
106 /*
107 * Even though this might sound confusing this in fact tells us
108 * that the compaction successfully isolated and migrated some
109 * pageblocks.
110 */
111 if (result == COMPACT_SUCCESS)
112 return true;
113
114 return false;
115}
116
117/* Compaction has failed and it doesn't make much sense to keep retrying. */
118static inline bool compaction_failed(enum compact_result result)
119{
120 /* All zones were scanned completely and still not result. */
121 if (result == COMPACT_COMPLETE)
122 return true;
123
124 return false;
125}
126
127/* Compaction needs reclaim to be performed first, so it can continue. */
128static inline bool compaction_needs_reclaim(enum compact_result result)
129{
130 /*
131 * Compaction backed off due to watermark checks for order-0
132 * so the regular reclaim has to try harder and reclaim something.
133 */
134 if (result == COMPACT_SKIPPED)
135 return true;
136
137 return false;
138}
139
140/*
141 * Compaction has backed off for some reason after doing some work or none
142 * at all. It might be throttling or lock contention. Retrying might be still
143 * worthwhile, but with a higher priority if allowed.
144 */
145static inline bool compaction_withdrawn(enum compact_result result)
146{
147 /*
148 * If compaction is deferred for high-order allocations, it is
149 * because sync compaction recently failed. If this is the case
150 * and the caller requested a THP allocation, we do not want
151 * to heavily disrupt the system, so we fail the allocation
152 * instead of entering direct reclaim.
153 */
154 if (result == COMPACT_DEFERRED)
155 return true;
156
157 /*
158 * If compaction in async mode encounters contention or blocks higher
159 * priority task we back off early rather than cause stalls.
160 */
161 if (result == COMPACT_CONTENDED)
162 return true;
163
164 /*
165 * Page scanners have met but we haven't scanned full zones so this
166 * is a back off in fact.
167 */
168 if (result == COMPACT_PARTIAL_SKIPPED)
169 return true;
170
171 return false;
172}
173
174
175bool compaction_zonelist_suitable(struct alloc_context *ac, int order,
176 int alloc_flags);
177
178extern int kcompactd_run(int nid);
179extern void kcompactd_stop(int nid);
180extern void wakeup_kcompactd(pg_data_t *pgdat, int order, int highest_zoneidx);
181
182#else
183static inline void reset_isolation_suitable(pg_data_t *pgdat)
184{
185}
186
187static inline enum compact_result compaction_suitable(struct zone *zone, int order,
188 int alloc_flags, int highest_zoneidx)
189{
190 return COMPACT_SKIPPED;
191}
192
193static inline bool compaction_made_progress(enum compact_result result)
194{
195 return false;
196}
197
198static inline bool compaction_failed(enum compact_result result)
199{
200 return false;
201}
202
203static inline bool compaction_needs_reclaim(enum compact_result result)
204{
205 return false;
206}
207
208static inline bool compaction_withdrawn(enum compact_result result)
209{
210 return true;
211}
212
213static inline int kcompactd_run(int nid)
214{
215 return 0;
216}
217static inline void kcompactd_stop(int nid)
218{
219}
220
221static inline void wakeup_kcompactd(pg_data_t *pgdat,
222 int order, int highest_zoneidx)
223{
224}
225
226#endif /* CONFIG_COMPACTION */
227
228struct node;
229#if defined(CONFIG_COMPACTION) && defined(CONFIG_SYSFS) && defined(CONFIG_NUMA)
230extern int compaction_register_node(struct node *node);
231extern void compaction_unregister_node(struct node *node);
232
233#else
234
235static inline int compaction_register_node(struct node *node)
236{
237 return 0;
238}
239
240static inline void compaction_unregister_node(struct node *node)
241{
242}
243#endif /* CONFIG_COMPACTION && CONFIG_SYSFS && CONFIG_NUMA */
244
245#endif /* _LINUX_COMPACTION_H */