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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 /* 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
61struct 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 */
68static 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
87extern int sysctl_compact_memory;
88extern int sysctl_compaction_handler(struct ctl_table *table, int write,
89 void __user *buffer, size_t *length, loff_t *ppos);
90extern int sysctl_extfrag_threshold;
91extern int sysctl_extfrag_handler(struct ctl_table *table, int write,
92 void __user *buffer, size_t *length, loff_t *ppos);
93extern int sysctl_compact_unevictable_allowed;
94
95extern int fragmentation_index(struct zone *zone, unsigned int order);
96extern 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);
99extern void reset_isolation_suitable(pg_data_t *pgdat);
100extern enum compact_result compaction_suitable(struct zone *zone, int order,
101 unsigned int alloc_flags, int classzone_idx);
102
103extern void defer_compaction(struct zone *zone, int order);
104extern bool compaction_deferred(struct zone *zone, int order);
105extern void compaction_defer_reset(struct zone *zone, int order,
106 bool alloc_success);
107extern bool compaction_restarting(struct zone *zone, int order);
108
109/* Compaction has made some progress and retrying makes sense */
110static 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. */
124static 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 */
137static 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
174bool compaction_zonelist_suitable(struct alloc_context *ac, int order,
175 int alloc_flags);
176
177extern int kcompactd_run(int nid);
178extern void kcompactd_stop(int nid);
179extern void wakeup_kcompactd(pg_data_t *pgdat, int order, int classzone_idx);
180
181#else
182static inline void reset_isolation_suitable(pg_data_t *pgdat)
183{
184}
185
186static 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
192static inline void defer_compaction(struct zone *zone, int order)
193{
194}
195
196static inline bool compaction_deferred(struct zone *zone, int order)
197{
198 return true;
199}
200
201static inline bool compaction_made_progress(enum compact_result result)
202{
203 return false;
204}
205
206static inline bool compaction_failed(enum compact_result result)
207{
208 return false;
209}
210
211static inline bool compaction_withdrawn(enum compact_result result)
212{
213 return true;
214}
215
216static inline int kcompactd_run(int nid)
217{
218 return 0;
219}
220static inline void kcompactd_stop(int nid)
221{
222}
223
224static 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)
231struct node;
232extern int compaction_register_node(struct node *node);
233extern void compaction_unregister_node(struct node *node);
234
235#else
236
237static inline int compaction_register_node(struct node *node)
238{
239 return 0;
240}
241
242static inline void compaction_unregister_node(struct node *node)
243{
244}
245#endif /* CONFIG_COMPACTION && CONFIG_SYSFS && CONFIG_NUMA */
246
247#endif /* _LINUX_COMPACTION_H */