• Home
  • Line#
  • Scopes#
  • Navigate#
  • Raw
  • Download
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  *
8  * The 'gfpmask' refers to the allocation we are currently trying to
9  * fulfil.
10  */
11 struct shrink_control {
12 	gfp_t gfp_mask;
13 
14 	/*
15 	 * How many objects scan_objects should scan and try to reclaim.
16 	 * This is reset before every call, so it is safe for callees
17 	 * to modify.
18 	 */
19 	unsigned long nr_to_scan;
20 
21 	/* shrink from these nodes */
22 	nodemask_t nodes_to_scan;
23 	/* current node being shrunk (for NUMA aware shrinkers) */
24 	int nid;
25 };
26 
27 #define SHRINK_STOP (~0UL)
28 /*
29  * A callback you can register to apply pressure to ageable caches.
30  *
31  * @count_objects should return the number of freeable items in the cache. If
32  * there are no objects to free or the number of freeable items cannot be
33  * determined, it should return 0. No deadlock checks should be done during the
34  * count callback - the shrinker relies on aggregating scan counts that couldn't
35  * be executed due to potential deadlocks to be run at a later call when the
36  * deadlock condition is no longer pending.
37  *
38  * @scan_objects will only be called if @count_objects returned a non-zero
39  * value for the number of freeable objects. The callout should scan the cache
40  * and attempt to free items from the cache. It should then return the number
41  * of objects freed during the scan, or SHRINK_STOP if progress cannot be made
42  * due to potential deadlocks. If SHRINK_STOP is returned, then no further
43  * attempts to call the @scan_objects will be made from the current reclaim
44  * context.
45  *
46  * @flags determine the shrinker abilities, like numa awareness
47  */
48 struct shrinker {
49 	unsigned long (*count_objects)(struct shrinker *,
50 				       struct shrink_control *sc);
51 	unsigned long (*scan_objects)(struct shrinker *,
52 				      struct shrink_control *sc);
53 
54 	int seeks;	/* seeks to recreate an obj */
55 	long batch;	/* reclaim batch size, 0 = default */
56 	unsigned long flags;
57 
58 	/* These are for internal use */
59 	struct list_head list;
60 	/* objs pending delete, per node */
61 	atomic_long_t *nr_deferred;
62 };
63 #define DEFAULT_SEEKS 2 /* A good number if you don't know better. */
64 
65 /* Flags */
66 #define SHRINKER_NUMA_AWARE (1 << 0)
67 
68 extern int register_shrinker(struct shrinker *);
69 extern void unregister_shrinker(struct shrinker *);
70 #endif
71