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 /* current node being shrunk (for NUMA aware shrinkers) */ 22 int nid; 23 24 /* current memcg being shrunk (for memcg aware shrinkers) */ 25 struct mem_cgroup *memcg; 26 }; 27 28 #define SHRINK_STOP (~0UL) 29 /* 30 * A callback you can register to apply pressure to ageable caches. 31 * 32 * @count_objects should return the number of freeable items in the cache. If 33 * there are no objects to free or the number of freeable items cannot be 34 * determined, it should return 0. No deadlock checks should be done during the 35 * count callback - the shrinker relies on aggregating scan counts that couldn't 36 * be executed due to potential deadlocks to be run at a later call when the 37 * deadlock condition is no longer pending. 38 * 39 * @scan_objects will only be called if @count_objects returned a non-zero 40 * value for the number of freeable objects. The callout should scan the cache 41 * and attempt to free items from the cache. It should then return the number 42 * of objects freed during the scan, or SHRINK_STOP if progress cannot be made 43 * due to potential deadlocks. If SHRINK_STOP is returned, then no further 44 * attempts to call the @scan_objects will be made from the current reclaim 45 * context. 46 * 47 * @flags determine the shrinker abilities, like numa awareness 48 */ 49 struct shrinker { 50 unsigned long (*count_objects)(struct shrinker *, 51 struct shrink_control *sc); 52 unsigned long (*scan_objects)(struct shrinker *, 53 struct shrink_control *sc); 54 55 int seeks; /* seeks to recreate an obj */ 56 long batch; /* reclaim batch size, 0 = default */ 57 unsigned long flags; 58 59 /* These are for internal use */ 60 struct list_head list; 61 /* objs pending delete, per node */ 62 atomic_long_t *nr_deferred; 63 }; 64 #define DEFAULT_SEEKS 2 /* A good number if you don't know better. */ 65 66 /* Flags */ 67 #define SHRINKER_NUMA_AWARE (1 << 0) 68 #define SHRINKER_MEMCG_AWARE (1 << 1) 69 70 extern int register_shrinker(struct shrinker *); 71 extern void unregister_shrinker(struct shrinker *); 72 #endif 73