summaryrefslogtreecommitdiff
path: root/include/linux/compaction.h
blob: 6fa0eea3f530016ac10321195004d2fbc04c23b2 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
/* SPDX-License-Identifier: GPL-2.0 */
#ifndef _LINUX_COMPACTION_H
#define _LINUX_COMPACTION_H

/*
 * Determines how hard direct compaction should try to succeed.
 * Lower value means higher priority, analogically to reclaim priority.
 */
enum compact_priority {
	COMPACT_PRIO_SYNC_FULL,
	MIN_COMPACT_PRIORITY = COMPACT_PRIO_SYNC_FULL,
	COMPACT_PRIO_SYNC_LIGHT,
	MIN_COMPACT_COSTLY_PRIORITY = COMPACT_PRIO_SYNC_LIGHT,
	DEF_COMPACT_PRIORITY = COMPACT_PRIO_SYNC_LIGHT,
	COMPACT_PRIO_ASYNC,
	INIT_COMPACT_PRIORITY = COMPACT_PRIO_ASYNC
};

/* Return values for compact_zone() and try_to_compact_pages() */
/* When adding new states, please adjust include/trace/events/compaction.h */
enum compact_result {
	/* For more detailed tracepoint output - internal to compaction */
	COMPACT_NOT_SUITABLE_ZONE,
	/*
	 * compaction didn't start as it was not possible or direct reclaim
	 * was more suitable
	 */
	COMPACT_SKIPPED,
	/* compaction didn't start as it was deferred due to past failures */
	COMPACT_DEFERRED,

	/* compaction not active last round */
	COMPACT_INACTIVE = COMPACT_DEFERRED,

	/* For more detailed tracepoint output - internal to compaction */
	COMPACT_NO_SUITABLE_PAGE,
	/* compaction should continue to another pageblock */
	COMPACT_CONTINUE,

	/*
	 * The full zone was compacted scanned but wasn't successfull to compact
	 * suitable pages.
	 */
	COMPACT_COMPLETE,
	/*
	 * direct compaction has scanned part of the zone but wasn't successfull
	 * to compact suitable pages.
	 */
	COMPACT_PARTIAL_SKIPPED,

	/* compaction terminated prematurely due to lock contentions */
	COMPACT_CONTENDED,

	/*
	 * direct compaction terminated after concluding that the allocation
	 * should now succeed
	 */
	COMPACT_SUCCESS,
};

struct alloc_context; /* in mm/internal.h */

/*
 * Number of free order-0 pages that should be available above given watermark
 * to make sure compaction has reasonable chance of not running out of free
 * pages that it needs to isolate as migration target during its work.
 */
static inline unsigned long compact_gap(unsigned int order)
{
	/*
	 * Although all the isolations for migration are temporary, compaction
	 * free scanner may have up to 1 << order pages on its list and then
	 * try to split an (order - 1) free page. At that point, a gap of
	 * 1 << order might not be enough, so it's safer to require twice that
	 * amount. Note that the number of pages on the list is also
	 * effectively limited by COMPACT_CLUSTER_MAX, as that's the maximum
	 * that the migrate scanner can have isolated on migrate list, and free
	 * scanner is only invoked when the number of isolated free pages is
	 * lower than that. But it's not worth to complicate the formula here
	 * as a bigger gap for higher orders than strictly necessary can also
	 * improve chances of compaction success.
	 */
	return 2UL << order;
}

#ifdef CONFIG_COMPACTION
extern int sysctl_compact_memory;
extern int sysctl_compaction_handler(struct ctl_table *table, int write,
			void *buffer, size_t *length, loff_t *ppos);
extern int sysctl_extfrag_threshold;
extern int sysctl_compact_unevictable_allowed;

extern int fragmentation_index(struct zone *zone, unsigned int order);
extern enum compact_result try_to_compact_pages(gfp_t gfp_mask,
		unsigned int order, unsigned int alloc_flags,
		const struct alloc_context *ac, enum compact_priority prio,
		struct page **page);
extern void reset_isolation_suitable(pg_data_t *pgdat);
extern enum compact_result compaction_suitable(struct zone *zone, int order,
		unsigned int alloc_flags, int highest_zoneidx);

extern void defer_compaction(struct zone *zone, int order);
extern bool compaction_deferred(struct zone *zone, int order);
extern void compaction_defer_reset(struct zone *zone, int order,
				bool alloc_success);
extern bool compaction_restarting(struct zone *zone, int order);

/* Compaction has made some progress and retrying makes sense */
static inline bool compaction_made_progress(enum compact_result result)
{
	/*
	 * Even though this might sound confusing this in fact tells us
	 * that the compaction successfully isolated and migrated some
	 * pageblocks.
	 */
	if (result == COMPACT_SUCCESS)
		return true;

	return false;
}

/* Compaction has failed and it doesn't make much sense to keep retrying. */
static inline bool compaction_failed(enum compact_result result)
{
	/* All zones were scanned completely and still not result. */
	if (result == COMPACT_COMPLETE)
		return true;

	return false;
}

/* Compaction needs reclaim to be performed first, so it can continue. */
static inline bool compaction_needs_reclaim(enum compact_result result)
{
	/*
	 * Compaction backed off due to watermark checks for order-0
	 * so the regular reclaim has to try harder and reclaim something.
	 */
	if (result == COMPACT_SKIPPED)
		return true;

	return false;
}

/*
 * Compaction has backed off for some reason after doing some work or none
 * at all. It might be throttling or lock contention. Retrying might be still
 * worthwhile, but with a higher priority if allowed.
 */
static inline bool compaction_withdrawn(enum compact_result result)
{
	/*
	 * If compaction is deferred for high-order allocations, it is
	 * because sync compaction recently failed. If this is the case
	 * and the caller requested a THP allocation, we do not want
	 * to heavily disrupt the system, so we fail the allocation
	 * instead of entering direct reclaim.
	 */
	if (result == COMPACT_DEFERRED)
		return true;

	/*
	 * If compaction in async mode encounters contention or blocks higher
	 * priority task we back off early rather than cause stalls.
	 */
	if (result == COMPACT_CONTENDED)
		return true;

	/*
	 * Page scanners have met but we haven't scanned full zones so this
	 * is a back off in fact.
	 */
	if (result == COMPACT_PARTIAL_SKIPPED)
		return true;

	return false;
}


bool compaction_zonelist_suitable(struct alloc_context *ac, int order,
					int alloc_flags);

extern int kcompactd_run(int nid);
extern void kcompactd_stop(int nid);
extern void wakeup_kcompactd(pg_data_t *pgdat, int order, int highest_zoneidx);

#else
static inline void reset_isolation_suitable(pg_data_t *pgdat)
{
}

static inline enum compact_result compaction_suitable(struct zone *zone, int order,
					int alloc_flags, int highest_zoneidx)
{
	return COMPACT_SKIPPED;
}

static inline void defer_compaction(struct zone *zone, int order)
{
}

static inline bool compaction_deferred(struct zone *zone, int order)
{
	return true;
}

static inline bool compaction_made_progress(enum compact_result result)
{
	return false;
}

static inline bool compaction_failed(enum compact_result result)
{
	return false;
}

static inline bool compaction_needs_reclaim(enum compact_result result)
{
	return false;
}

static inline bool compaction_withdrawn(enum compact_result result)
{
	return true;
}

static inline int kcompactd_run(int nid)
{
	return 0;
}
static inline void kcompactd_stop(int nid)
{
}

static inline void wakeup_kcompactd(pg_data_t *pgdat,
				int order, int highest_zoneidx)
{
}

#endif /* CONFIG_COMPACTION */

struct node;
#if defined(CONFIG_COMPACTION) && defined(CONFIG_SYSFS) && defined(CONFIG_NUMA)
extern int compaction_register_node(struct node *node);
extern void compaction_unregister_node(struct node *node);

#else

static inline int compaction_register_node(struct node *node)
{
	return 0;
}

static inline void compaction_unregister_node(struct node *node)
{
}
#endif /* CONFIG_COMPACTION && CONFIG_SYSFS && CONFIG_NUMA */

#endif /* _LINUX_COMPACTION_H */