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 struct 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 * 24 * The 'gfpmask' refers to the allocation we are currently trying to 25 * fulfil. 26 * 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. 29 */ 30 struct shrinker { 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 */ 34 35 /* These are for internal use */ 36 struct list_head list; 37 atomic_long_t nr_in_batch; /* objs pending delete */ 38 }; 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 *); 42 #endif 43