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 /* 22 * How many objects did scan_objects process? 23 * This defaults to nr_to_scan before every call, but the callee 24 * should track its actual progress. 25 */ 26 unsigned long nr_scanned; 27 28 /* current node being shrunk (for NUMA aware shrinkers) */ 29 int nid; 30 31 /* current memcg being shrunk (for memcg aware shrinkers) */ 32 struct mem_cgroup *memcg; 33 }; 34 35 #define SHRINK_STOP (~0UL) 36 /* 37 * A callback you can register to apply pressure to ageable caches. 38 * 39 * @count_objects should return the number of freeable items in the cache. If 40 * there are no objects to free or the number of freeable items cannot be 41 * determined, it should return 0. No deadlock checks should be done during the 42 * count callback - the shrinker relies on aggregating scan counts that couldn't 43 * be executed due to potential deadlocks to be run at a later call when the 44 * deadlock condition is no longer pending. 45 * 46 * @scan_objects will only be called if @count_objects returned a non-zero 47 * value for the number of freeable objects. The callout should scan the cache 48 * and attempt to free items from the cache. It should then return the number 49 * of objects freed during the scan, or SHRINK_STOP if progress cannot be made 50 * due to potential deadlocks. If SHRINK_STOP is returned, then no further 51 * attempts to call the @scan_objects will be made from the current reclaim 52 * context. 53 * 54 * @flags determine the shrinker abilities, like numa awareness 55 */ 56 struct shrinker { 57 unsigned long (*count_objects)(struct shrinker *, 58 struct shrink_control *sc); 59 unsigned long (*scan_objects)(struct shrinker *, 60 struct shrink_control *sc); 61 62 int seeks; /* seeks to recreate an obj */ 63 long batch; /* reclaim batch size, 0 = default */ 64 unsigned long flags; 65 66 /* These are for internal use */ 67 struct list_head list; 68 /* objs pending delete, per node */ 69 atomic_long_t *nr_deferred; 70 }; 71 #define DEFAULT_SEEKS 2 /* A good number if you don't know better. */ 72 73 /* Flags */ 74 #define SHRINKER_NUMA_AWARE (1 << 0) 75 #define SHRINKER_MEMCG_AWARE (1 << 1) 76 77 extern int register_shrinker(struct shrinker *); 78 extern void unregister_shrinker(struct shrinker *); 79 #endif 80