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
84
85extern unsigned int extfrag_for_order(struct zone *zone, unsigned int order);
86extern int fragmentation_index(struct zone *zone, unsigned int order);
87extern 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);
91extern void reset_isolation_suitable(pg_data_t *pgdat);
92extern bool compaction_suitable(struct zone *zone, int order,
93 int highest_zoneidx);
94
95extern void compaction_defer_reset(struct zone *zone, int order,
96 bool alloc_success);
97
98bool compaction_zonelist_suitable(struct alloc_context *ac, int order,
99 int alloc_flags);
100
101extern void __meminit kcompactd_run(int nid);
102extern void __meminit kcompactd_stop(int nid);
103extern void wakeup_kcompactd(pg_data_t *pgdat, int order, int highest_zoneidx);
104
105#else
106static inline void reset_isolation_suitable(pg_data_t *pgdat)
107{
108}
109
110static inline bool compaction_suitable(struct zone *zone, int order,
111 int highest_zoneidx)
112{
113 return false;
114}
115
116static inline void kcompactd_run(int nid)
117{
118}
119static inline void kcompactd_stop(int nid)
120{
121}
122
123static inline void wakeup_kcompactd(pg_data_t *pgdat,
124 int order, int highest_zoneidx)
125{
126}
127
128#endif /* CONFIG_COMPACTION */
129
130struct node;
131#if defined(CONFIG_COMPACTION) && defined(CONFIG_SYSFS) && defined(CONFIG_NUMA)
132extern int compaction_register_node(struct node *node);
133extern void compaction_unregister_node(struct node *node);
134
135#else
136
137static inline int compaction_register_node(struct node *node)
138{
139 return 0;
140}
141
142static inline void compaction_unregister_node(struct node *node)
143{
144}
145#endif /* CONFIG_COMPACTION && CONFIG_SYSFS && CONFIG_NUMA */
146
147#endif /* _LINUX_COMPACTION_H */
148

source code of linux/include/linux/compaction.h