1/* SPDX-License-Identifier: GPL-2.0 */
 2#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.
 8 *
 9 * The 'gfpmask' refers to the allocation we are currently trying to
10 * fulfil.
11 */
12struct shrink_control {
13	gfp_t gfp_mask;
14
15	/* current node being shrunk (for NUMA aware shrinkers) */
16	int nid;
17
18	/*
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	 */
23	unsigned long nr_to_scan;
24
25	/*
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
32	/* current memcg being shrunk (for memcg aware shrinkers) */
33	struct mem_cgroup *memcg;
34};
35
36#define SHRINK_STOP (~0UL)
37#define SHRINK_EMPTY (~0UL - 1)
38/*
39 * A callback you can register to apply pressure to ageable caches.
40 *
41 * @count_objects should return the number of freeable items in the cache. If
42 * 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
46 * 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.
49 *
50 * @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.
57 *
58 * @flags determine the shrinker abilities, like numa awareness
 
59 */
60struct shrinker {
61	unsigned long (*count_objects)(struct shrinker *,
62				       struct shrink_control *sc);
63	unsigned long (*scan_objects)(struct shrinker *,
64				      struct shrink_control *sc);
65
66	long batch;	/* reclaim batch size, 0 = default */
67	int seeks;	/* seeks to recreate an obj */
68	unsigned flags;
69
70	/* These are for internal use */
71	struct list_head list;
72#ifdef CONFIG_MEMCG
73	/* ID in shrinker_idr */
74	int id;
75#endif
76	/* objs pending delete, per node */
77	atomic_long_t *nr_deferred;
78};
79#define DEFAULT_SEEKS 2 /* A good number if you don't know better. */
80
81/* Flags */
82#define SHRINKER_NUMA_AWARE	(1 << 0)
83#define SHRINKER_MEMCG_AWARE	(1 << 1)
84/*
85 * It just makes sense when the shrinker is also MEMCG_AWARE for now,
86 * non-MEMCG_AWARE shrinker should not have this flag set.
87 */
88#define SHRINKER_NONSLAB	(1 << 2)
89
90extern int prealloc_shrinker(struct shrinker *shrinker);
91extern void register_shrinker_prepared(struct shrinker *shrinker);
92extern int register_shrinker(struct shrinker *shrinker);
93extern void unregister_shrinker(struct shrinker *shrinker);
94extern void free_prealloced_shrinker(struct shrinker *shrinker);
95#endif

 
 1#ifndef _LINUX_SHRINKER_H
 2#define _LINUX_SHRINKER_H
 3
 4/*
 5 * This struct is used to pass information from page reclaim to the shrinkers.
 6 * We consolidate the values for easier extention later.
 
 
 
 7 */
 8struct shrink_control {
 9	gfp_t gfp_mask;
10
11	/* How many slab objects shrinker() should scan and try to reclaim */
 
 
 
 
 
 
 
12	unsigned long nr_to_scan;
 
 
 
 
 
 
 
 
 
 
13};
14
 
 
15/*
16 * A callback you can register to apply pressure to ageable caches.
17 *
18 * 'sc' is passed shrink_control which includes a count 'nr_to_scan'
19 * and a 'gfpmask'.  It should look through the least-recently-used
20 * 'nr_to_scan' entries and attempt to free them up.  It should return
21 * the number of objects which remain in the cache.  If it returns -1, it means
22 * it cannot do any scanning at this time (eg. there is a risk of deadlock).
23 * The callback must not return -1 if nr_to_scan is zero.
 
 
24 *
25 * The 'gfpmask' refers to the allocation we are currently trying to
26 * fulfil.
 
 
 
 
 
27 *
28 * Note that 'shrink' will be passed nr_to_scan == 0 when the VM is
29 * querying the cache size, so a fastpath for that case is appropriate.
30 */
31struct shrinker {
32	int (*shrink)(struct shrinker *, struct shrink_control *sc);
 
 
 
 
 
33	int seeks;	/* seeks to recreate an obj */
34	long batch;	/* reclaim batch size, 0 = default */
35
36	/* These are for internal use */
37	struct list_head list;
38	atomic_long_t nr_in_batch; /* objs pending delete */
 
 
 
 
 
39};
40#define DEFAULT_SEEKS 2 /* A good number if you don't know better. */
41extern void register_shrinker(struct shrinker *);
42extern void unregister_shrinker(struct shrinker *);
 
 
 
 
 
 
 
 
 
 
 
 
 
43#endif