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