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

#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;

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

#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)

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