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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: