[mirror_ubuntu-bionic-kernel.git] / include / linux / shrinker.h

/* SPDX-License-Identifier: GPL-2.0 */
#ifndef _LINUX_SHRINKER_H
#define _LINUX_SHRINKER_H

/*
 * This struct is used to pass information from page reclaim to the shrinkers.
 * We consolidate the values for easier extention later.
 *
 * The 'gfpmask' refers to the allocation we are currently trying to
 * fulfil.
 */
struct shrink_control {
	gfp_t gfp_mask;

	/*
	 * How many objects scan_objects should scan and try to reclaim.
	 * This is reset before every call, so it is safe for callees
	 * to modify.
	 */
	unsigned long nr_to_scan;

	/*
	 * How many objects did scan_objects process?
	 * This defaults to nr_to_scan before every call, but the callee
	 * should track its actual progress.
	 */
	unsigned long nr_scanned;

	/* current node being shrunk (for NUMA aware shrinkers) */
	int nid;

	/* current memcg being shrunk (for memcg aware shrinkers) */
	struct mem_cgroup *memcg;
};

#define SHRINK_STOP (~0UL)
/*
 * A callback you can register to apply pressure to ageable caches.
 *
 * @count_objects should return the number of freeable items in the cache. If
 * there are no objects to free or the number of freeable items cannot be
 * determined, it should return 0. No deadlock checks should be done during the
 * count callback - the shrinker relies on aggregating scan counts that couldn't
 * be executed due to potential deadlocks to be run at a later call when the
 * deadlock condition is no longer pending.
 *
 * @scan_objects will only be called if @count_objects returned a non-zero
 * value for the number of freeable objects. The callout should scan the cache
 * and attempt to free items from the cache. It should then return the number
 * of objects freed during the scan, or SHRINK_STOP if progress cannot be made
 * due to potential deadlocks. If SHRINK_STOP is returned, then no further
 * attempts to call the @scan_objects will be made from the current reclaim
 * context.
 *
 * @flags determine the shrinker abilities, like numa awareness
 */
struct shrinker {
	unsigned long (*count_objects)(struct shrinker *,
				       struct shrink_control *sc);
	unsigned long (*scan_objects)(struct shrinker *,
				      struct shrink_control *sc);

	int seeks;	/* seeks to recreate an obj */
	long batch;	/* reclaim batch size, 0 = default */
	unsigned long flags;

	/* These are for internal use */
	struct list_head list;
	/* objs pending delete, per node */
	atomic_long_t *nr_deferred;
};
#define DEFAULT_SEEKS 2 /* A good number if you don't know better. */

/* Flags */
#define SHRINKER_NUMA_AWARE	(1 << 0)
#define SHRINKER_MEMCG_AWARE	(1 << 1)

extern int prealloc_shrinker(struct shrinker *shrinker);
extern void register_shrinker_prepared(struct shrinker *shrinker);
extern int register_shrinker(struct shrinker *shrinker);
extern void unregister_shrinker(struct shrinker *shrinker);
extern void free_prealloced_shrinker(struct shrinker *shrinker);
#endif
Commit	Line	Data
	1	/* SPDX-License-Identifier: GPL-2.0 */
	2	#ifndef _LINUX_SHRINKER_H
	3	#define _LINUX_SHRINKER_H
	4
	5	/*
	6	* This struct is used to pass information from page reclaim to the shrinkers.
	7	* We consolidate the values for easier extention later.
	8	*
	9	* The 'gfpmask' refers to the allocation we are currently trying to
	10	* fulfil.
	11	*/
	12	struct shrink_control {
	13	gfp_t gfp_mask;
	14
	15	/*
	16	* How many objects scan_objects should scan and try to reclaim.
	17	* This is reset before every call, so it is safe for callees
	18	* to modify.
	19	*/
	20	unsigned long nr_to_scan;
	21
	22	/*
	23	* How many objects did scan_objects process?
	24	* This defaults to nr_to_scan before every call, but the callee
	25	* should track its actual progress.
	26	*/
	27	unsigned long nr_scanned;
	28
	29	/* current node being shrunk (for NUMA aware shrinkers) */
	30	int nid;
	31
	32	/* current memcg being shrunk (for memcg aware shrinkers) */
	33	struct mem_cgroup *memcg;
	34	};
	35
	36	#define SHRINK_STOP (~0UL)
	37	/*
	38	* A callback you can register to apply pressure to ageable caches.
	39	*
	40	* @count_objects should return the number of freeable items in the cache. If
	41	* there are no objects to free or the number of freeable items cannot be
	42	* determined, it should return 0. No deadlock checks should be done during the
	43	* count callback - the shrinker relies on aggregating scan counts that couldn't
	44	* be executed due to potential deadlocks to be run at a later call when the
	45	* deadlock condition is no longer pending.
	46	*
	47	* @scan_objects will only be called if @count_objects returned a non-zero
	48	* value for the number of freeable objects. The callout should scan the cache
	49	* and attempt to free items from the cache. It should then return the number
	50	* of objects freed during the scan, or SHRINK_STOP if progress cannot be made
	51	* due to potential deadlocks. If SHRINK_STOP is returned, then no further
	52	* attempts to call the @scan_objects will be made from the current reclaim
	53	* context.
	54	*
	55	* @flags determine the shrinker abilities, like numa awareness
	56	*/
	57	struct shrinker {
	58	unsigned long (count_objects)(struct shrinker ,
	59	struct shrink_control *sc);
	60	unsigned long (scan_objects)(struct shrinker ,
	61	struct shrink_control *sc);
	62
	63	int seeks; /* seeks to recreate an obj */
	64	long batch; /* reclaim batch size, 0 = default */
	65	unsigned long flags;
	66
	67	/* These are for internal use */
	68	struct list_head list;
	69	/* objs pending delete, per node */
	70	atomic_long_t *nr_deferred;
	71	};
	72	#define DEFAULT_SEEKS 2 /* A good number if you don't know better. */
	73
	74	/* Flags */
	75	#define SHRINKER_NUMA_AWARE (1 << 0)
	76	#define SHRINKER_MEMCG_AWARE (1 << 1)
	77
	78	extern int prealloc_shrinker(struct shrinker *shrinker);
	79	extern void register_shrinker_prepared(struct shrinker *shrinker);
	80	extern int register_shrinker(struct shrinker *shrinker);
	81	extern void unregister_shrinker(struct shrinker *shrinker);
	82	extern void free_prealloced_shrinker(struct shrinker *shrinker);
	83	#endif