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Greg Kroah-Hartmanb2441312017-11-01 15:07:57 +01001/* SPDX-License-Identifier: GPL-2.0 */
Dave Chinnerb0d40c92011-07-08 14:14:42 +10002#ifndef _LINUX_SHRINKER_H
3#define _LINUX_SHRINKER_H
4
5/*
6 * This struct is used to pass information from page reclaim to the shrinkers.
7 * We consolidate the values for easier extention later.
Dave Chinner24f7c6b2013-08-28 10:17:56 +10008 *
9 * The 'gfpmask' refers to the allocation we are currently trying to
10 * fulfil.
Dave Chinnerb0d40c92011-07-08 14:14:42 +100011 */
12struct shrink_control {
13 gfp_t gfp_mask;
14
Kirill Tkhai92be7752018-08-21 21:51:53 -070015 /* current node being shrunk (for NUMA aware shrinkers) */
16 int nid;
17
Dave Chinnera0b02132013-08-28 10:18:16 +100018 /*
19 * How many objects scan_objects should scan and try to reclaim.
20 * This is reset before every call, so it is safe for callees
21 * to modify.
22 */
Dave Chinnerb0d40c92011-07-08 14:14:42 +100023 unsigned long nr_to_scan;
Dave Chinner0ce3d742013-08-28 10:18:03 +100024
Chris Wilsond460acb2017-09-06 16:19:26 -070025 /*
26 * How many objects did scan_objects process?
27 * This defaults to nr_to_scan before every call, but the callee
28 * should track its actual progress.
29 */
30 unsigned long nr_scanned;
31
Vladimir Davydovcb731d62015-02-12 14:58:54 -080032 /* current memcg being shrunk (for memcg aware shrinkers) */
33 struct mem_cgroup *memcg;
Dave Chinnerb0d40c92011-07-08 14:14:42 +100034};
35
Dave Chinner24f7c6b2013-08-28 10:17:56 +100036#define SHRINK_STOP (~0UL)
Kirill Tkhai9b996462018-08-17 15:48:21 -070037#define SHRINK_EMPTY (~0UL - 1)
Dave Chinnerb0d40c92011-07-08 14:14:42 +100038/*
39 * A callback you can register to apply pressure to ageable caches.
40 *
Dave Chinner24f7c6b2013-08-28 10:17:56 +100041 * @count_objects should return the number of freeable items in the cache. If
Kirill Tkhai9b996462018-08-17 15:48:21 -070042 * there are no objects to free, it should return SHRINK_EMPTY, while 0 is
43 * returned in cases of the number of freeable items cannot be determined
44 * or shrinker should skip this cache for this time (e.g., their number
45 * is below shrinkable limit). No deadlock checks should be done during the
Dave Chinner24f7c6b2013-08-28 10:17:56 +100046 * count callback - the shrinker relies on aggregating scan counts that couldn't
47 * be executed due to potential deadlocks to be run at a later call when the
48 * deadlock condition is no longer pending.
Dave Chinnerb0d40c92011-07-08 14:14:42 +100049 *
Dave Chinner24f7c6b2013-08-28 10:17:56 +100050 * @scan_objects will only be called if @count_objects returned a non-zero
51 * value for the number of freeable objects. The callout should scan the cache
52 * and attempt to free items from the cache. It should then return the number
53 * of objects freed during the scan, or SHRINK_STOP if progress cannot be made
54 * due to potential deadlocks. If SHRINK_STOP is returned, then no further
55 * attempts to call the @scan_objects will be made from the current reclaim
56 * context.
Glauber Costa1d3d4432013-08-28 10:18:04 +100057 *
58 * @flags determine the shrinker abilities, like numa awareness
Dave Chinnerb0d40c92011-07-08 14:14:42 +100059 */
60struct shrinker {
Dave Chinner24f7c6b2013-08-28 10:17:56 +100061 unsigned long (*count_objects)(struct shrinker *,
62 struct shrink_control *sc);
63 unsigned long (*scan_objects)(struct shrinker *,
64 struct shrink_control *sc);
65
Dave Chinnerb0d40c92011-07-08 14:14:42 +100066 long batch; /* reclaim batch size, 0 = default */
Kirill Tkhaie50ef892018-08-21 21:51:57 -070067 int seeks; /* seeks to recreate an obj */
68 unsigned flags;
Dave Chinnerb0d40c92011-07-08 14:14:42 +100069
70 /* These are for internal use */
71 struct list_head list;
Kirill Tkhaib4c2b232018-08-17 15:47:29 -070072#ifdef CONFIG_MEMCG_KMEM
73 /* ID in shrinker_idr */
74 int id;
75#endif
Glauber Costa1d3d4432013-08-28 10:18:04 +100076 /* objs pending delete, per node */
77 atomic_long_t *nr_deferred;
Dave Chinnerb0d40c92011-07-08 14:14:42 +100078};
79#define DEFAULT_SEEKS 2 /* A good number if you don't know better. */
Glauber Costa1d3d4432013-08-28 10:18:04 +100080
81/* Flags */
Vladimir Davydovcb731d62015-02-12 14:58:54 -080082#define SHRINKER_NUMA_AWARE (1 << 0)
83#define SHRINKER_MEMCG_AWARE (1 << 1)
Glauber Costa1d3d4432013-08-28 10:18:04 +100084
Tetsuo Handa8e049442018-04-04 19:53:07 +090085extern int prealloc_shrinker(struct shrinker *shrinker);
86extern void register_shrinker_prepared(struct shrinker *shrinker);
87extern int register_shrinker(struct shrinker *shrinker);
88extern void unregister_shrinker(struct shrinker *shrinker);
89extern void free_prealloced_shrinker(struct shrinker *shrinker);
Dave Chinnerb0d40c92011-07-08 14:14:42 +100090#endif