1 #ifndef _LINUX_SHRINKER_H
2 #define _LINUX_SHRINKER_H
5 * This struct is used to pass information from page reclaim to the shrinkers.
6 * We consolidate the values for easier extention later.
8 struct shrink_control {
11 /* How many slab objects shrinker() should scan and try to reclaim */
12 unsigned long nr_to_scan;
16 * A callback you can register to apply pressure to ageable caches.
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).
24 * The 'gfpmask' refers to the allocation we are currently trying to
27 * Note that 'shrink' will be passed nr_to_scan == 0 when the VM is
28 * querying the cache size, so a fastpath for that case is appropriate.
31 int (*shrink)(struct shrinker *, struct shrink_control *sc);
32 int seeks; /* seeks to recreate an obj */
33 long batch; /* reclaim batch size, 0 = default */
35 /* These are for internal use */
36 struct list_head list;
37 long nr; /* objs pending delete */
39 #define DEFAULT_SEEKS 2 /* A good number if you don't know better. */
40 extern void register_shrinker(struct shrinker *);
41 extern void unregister_shrinker(struct shrinker *);