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_compact_unevictable_allowed;
92
93extern int fragmentation_index(struct zone *zone, unsigned int order);
94extern 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 struct page **page);
98extern void reset_isolation_suitable(pg_data_t *pgdat);
99extern enum compact_result compaction_suitable(struct zone *zone, int order,
100 unsigned int alloc_flags, int classzone_idx);
101
102extern void defer_compaction(struct zone *zone, int order);
103extern bool compaction_deferred(struct zone *zone, int order);
104extern void compaction_defer_reset(struct zone *zone, int order,
105 bool alloc_success);
106extern bool compaction_restarting(struct zone *zone, int order);
107
108/* Compaction has made some progress and retrying makes sense */
109static inline bool compaction_made_progress(enum compact_result result)
110{
111 /*
112 * Even though this might sound confusing this in fact tells us
113 * that the compaction successfully isolated and migrated some
114 * pageblocks.
115 */
116 if (result == COMPACT_SUCCESS)
117 return true;
118
119 return false;
120}
121
122/* Compaction has failed and it doesn't make much sense to keep retrying. */
123static inline bool compaction_failed(enum compact_result result)
124{
125 /* All zones were scanned completely and still not result. */
126 if (result == COMPACT_COMPLETE)
127 return true;
128
129 return false;
130}
131
132/*
133 * Compaction has backed off for some reason. It might be throttling or
134 * lock contention. Retrying is still worthwhile.
135 */
136static inline bool compaction_withdrawn(enum compact_result result)
137{
138 /*
139 * Compaction backed off due to watermark checks for order-0
140 * so the regular reclaim has to try harder and reclaim something.
141 */
142 if (result == COMPACT_SKIPPED)
143 return true;
144
145 /*
146 * If compaction is deferred for high-order allocations, it is
147 * because sync compaction recently failed. If this is the case
148 * and the caller requested a THP allocation, we do not want
149 * to heavily disrupt the system, so we fail the allocation
150 * instead of entering direct reclaim.
151 */
152 if (result == COMPACT_DEFERRED)
153 return true;
154
155 /*
156 * If compaction in async mode encounters contention or blocks higher
157 * priority task we back off early rather than cause stalls.
158 */
159 if (result == COMPACT_CONTENDED)
160 return true;
161
162 /*
163 * Page scanners have met but we haven't scanned full zones so this
164 * is a back off in fact.
165 */
166 if (result == COMPACT_PARTIAL_SKIPPED)
167 return true;
168
169 return false;
170}
171
172
173bool compaction_zonelist_suitable(struct alloc_context *ac, int order,
174 int alloc_flags);
175
176extern int kcompactd_run(int nid);
177extern void kcompactd_stop(int nid);
178extern void wakeup_kcompactd(pg_data_t *pgdat, int order, int classzone_idx);
179
180#else
181static inline void reset_isolation_suitable(pg_data_t *pgdat)
182{
183}
184
185static inline enum compact_result compaction_suitable(struct zone *zone, int order,
186 int alloc_flags, int classzone_idx)
187{
188 return COMPACT_SKIPPED;
189}
190
191static inline void defer_compaction(struct zone *zone, int order)
192{
193}
194
195static inline bool compaction_deferred(struct zone *zone, int order)
196{
197 return true;
198}
199
200static inline bool compaction_made_progress(enum compact_result result)
201{
202 return false;
203}
204
205static inline bool compaction_failed(enum compact_result result)
206{
207 return false;
208}
209
210static inline bool compaction_withdrawn(enum compact_result result)
211{
212 return true;
213}
214
215static inline int kcompactd_run(int nid)
216{
217 return 0;
218}
219static inline void kcompactd_stop(int nid)
220{
221}
222
223static inline void wakeup_kcompactd(pg_data_t *pgdat, int order, int classzone_idx)
224{
225}
226
227#endif /* CONFIG_COMPACTION */
228
229struct node;
230#if defined(CONFIG_COMPACTION) && defined(CONFIG_SYSFS) && defined(CONFIG_NUMA)
231extern int compaction_register_node(struct node *node);
232extern void compaction_unregister_node(struct node *node);
233
234#else
235
236static inline int compaction_register_node(struct node *node)
237{
238 return 0;
239}
240
241static inline void compaction_unregister_node(struct node *node)
242{
243}
244#endif /* CONFIG_COMPACTION && CONFIG_SYSFS && CONFIG_NUMA */
245
246#endif /* _LINUX_COMPACTION_H */
247