[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;

	/*
	 * 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 register_shrinker(struct shrinker *);
extern void unregister_shrinker(struct shrinker *);
#endif
Commit	Line	Data
b0d40c92 DC	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.
24f7c6b9 DC	7	*
	8	* The 'gfpmask' refers to the allocation we are currently trying to
	9	* fulfil.
b0d40c92 DC	10	*/
	11	struct shrink_control {
	12	gfp_t gfp_mask;
	13
a0b02131 DC	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	*/
b0d40c92	19	unsigned long nr_to_scan;
0ce3d744	20
d460acb5 CW	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
1d3d4437 GC	28	/* current node being shrunk (for NUMA aware shrinkers) */
1d3d4437 GC	29	int nid;
cb731d6c VD	30
	31	/* current memcg being shrunk (for memcg aware shrinkers) */
	32	struct mem_cgroup *memcg;
b0d40c92 DC	33	};
b0d40c92 DC	34
24f7c6b9	35	#define SHRINK_STOP (~0UL)
b0d40c92 DC	36	/*
	37	* A callback you can register to apply pressure to ageable caches.
	38	*
24f7c6b9 DC	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.
b0d40c92	45	*
24f7c6b9 DC	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.
1d3d4437 GC	53	*
1d3d4437 GC	54	* @flags determine the shrinker abilities, like numa awareness
b0d40c92 DC	55	*/
b0d40c92 DC	56	struct shrinker {
24f7c6b9 DC	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
b0d40c92 DC	62	int seeks; /* seeks to recreate an obj */
b0d40c92 DC	63	long batch; /* reclaim batch size, 0 = default */
1d3d4437	64	unsigned long flags;
b0d40c92 DC	65
	66	/* These are for internal use */
	67	struct list_head list;
1d3d4437 GC	68	/* objs pending delete, per node */
1d3d4437 GC	69	atomic_long_t *nr_deferred;
b0d40c92 DC	70	};
b0d40c92 DC	71	#define DEFAULT_SEEKS 2 /* A good number if you don't know better. */
1d3d4437 GC	72
1d3d4437 GC	73	/* Flags */
cb731d6c VD	74	#define SHRINKER_NUMA_AWARE (1 << 0)
cb731d6c VD	75	#define SHRINKER_MEMCG_AWARE (1 << 1)
1d3d4437 GC	76
1d3d4437 GC	77	extern int register_shrinker(struct shrinker *);
b0d40c92 DC	78	extern void unregister_shrinker(struct shrinker *);
b0d40c92 DC	79	#endif