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1#ifndef _LINUX_COMPACTION_H
2#define _LINUX_COMPACTION_H
3
4/*
5 * Determines how hard direct compaction should try to succeed.
6 * Lower value means higher priority, analogically to reclaim priority.
7 */
8enum compact_priority {
9 COMPACT_PRIO_SYNC_FULL,
10 MIN_COMPACT_PRIORITY = COMPACT_PRIO_SYNC_FULL,
11 COMPACT_PRIO_SYNC_LIGHT,
12 MIN_COMPACT_COSTLY_PRIORITY = COMPACT_PRIO_SYNC_LIGHT,
13 DEF_COMPACT_PRIORITY = COMPACT_PRIO_SYNC_LIGHT,
14 COMPACT_PRIO_ASYNC,
15 INIT_COMPACT_PRIORITY = COMPACT_PRIO_ASYNC
16};
17
18/* Return values for compact_zone() and try_to_compact_pages() */
19/* When adding new states, please adjust include/trace/events/compaction.h */
20enum compact_result {
21 /* For more detailed tracepoint output - internal to compaction */
22 COMPACT_NOT_SUITABLE_ZONE,
23 /*
24 * compaction didn't start as it was not possible or direct reclaim
25 * was more suitable
26 */
27 COMPACT_SKIPPED,
28 /* compaction didn't start as it was deferred due to past failures */
29 COMPACT_DEFERRED,
30
31 /* compaction not active last round */
32 COMPACT_INACTIVE = COMPACT_DEFERRED,
33
34 /* For more detailed tracepoint output - internal to compaction */
35 COMPACT_NO_SUITABLE_PAGE,
36 /* compaction should continue to another pageblock */
37 COMPACT_CONTINUE,
38
39 /*
40 * The full zone was compacted scanned but wasn't successfull to compact
41 * suitable pages.
42 */
43 COMPACT_COMPLETE,
44 /*
45 * direct compaction has scanned part of the zone but wasn't successfull
46 * to compact suitable pages.
47 */
48 COMPACT_PARTIAL_SKIPPED,
49
50 /* compaction terminated prematurely due to lock contentions */
51 COMPACT_CONTENDED,
52
53 /*
54 * direct compaction terminated after concluding that the allocation
55 * should now succeed
56 */
57 COMPACT_SUCCESS,
58};
59
60struct alloc_context; /* in mm/internal.h */
61
62/*
63 * Number of free order-0 pages that should be available above given watermark
64 * to make sure compaction has reasonable chance of not running out of free
65 * pages that it needs to isolate as migration target during its work.
66 */
67static inline unsigned long compact_gap(unsigned int order)
68{
69 /*
70 * Although all the isolations for migration are temporary, compaction
71 * free scanner may have up to 1 << order pages on its list and then
72 * try to split an (order - 1) free page. At that point, a gap of
73 * 1 << order might not be enough, so it's safer to require twice that
74 * amount. Note that the number of pages on the list is also
75 * effectively limited by COMPACT_CLUSTER_MAX, as that's the maximum
76 * that the migrate scanner can have isolated on migrate list, and free
77 * scanner is only invoked when the number of isolated free pages is
78 * lower than that. But it's not worth to complicate the formula here
79 * as a bigger gap for higher orders than strictly necessary can also
80 * improve chances of compaction success.
81 */
82 return 2UL << order;
83}
84
85#ifdef CONFIG_COMPACTION
86extern int sysctl_compact_memory;
87extern int sysctl_compaction_handler(struct ctl_table *table, int write,
88 void __user *buffer, size_t *length, loff_t *ppos);
89extern int sysctl_extfrag_threshold;
90extern int sysctl_extfrag_handler(struct ctl_table *table, int write,
91 void __user *buffer, size_t *length, loff_t *ppos);
92extern int sysctl_compact_unevictable_allowed;
93
94extern int fragmentation_index(struct zone *zone, unsigned int order);
95extern enum compact_result try_to_compact_pages(gfp_t gfp_mask,
96 unsigned int order, unsigned int alloc_flags,
97 const struct alloc_context *ac, enum compact_priority prio);
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
229#if defined(CONFIG_COMPACTION) && defined(CONFIG_SYSFS) && defined(CONFIG_NUMA)
230struct node;
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 */