161 lines
4.9 KiB
C
161 lines
4.9 KiB
C
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/* SPDX-License-Identifier: GPL-2.0 */
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#ifndef _LINUX_SHRINKER_H
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#define _LINUX_SHRINKER_H
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#include <linux/atomic.h>
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#include <linux/types.h>
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#include <linux/refcount.h>
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#include <linux/completion.h>
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#define SHRINKER_UNIT_BITS BITS_PER_LONG
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/*
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* Bitmap and deferred work of shrinker::id corresponding to memcg-aware
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* shrinkers, which have elements charged to the memcg.
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*/
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struct shrinker_info_unit {
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atomic_long_t nr_deferred[SHRINKER_UNIT_BITS];
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DECLARE_BITMAP(map, SHRINKER_UNIT_BITS);
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};
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struct shrinker_info {
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struct rcu_head rcu;
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int map_nr_max;
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struct shrinker_info_unit *unit[];
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};
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/*
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* This struct is used to pass information from page reclaim to the shrinkers.
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* We consolidate the values for easier extension later.
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*
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* The 'gfpmask' refers to the allocation we are currently trying to
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* fulfil.
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*/
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struct shrink_control {
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gfp_t gfp_mask;
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/* current node being shrunk (for NUMA aware shrinkers) */
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int nid;
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/*
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* How many objects scan_objects should scan and try to reclaim.
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* This is reset before every call, so it is safe for callees
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* to modify.
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*/
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unsigned long nr_to_scan;
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/*
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* How many objects did scan_objects process?
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* This defaults to nr_to_scan before every call, but the callee
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* should track its actual progress.
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*/
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unsigned long nr_scanned;
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/* current memcg being shrunk (for memcg aware shrinkers) */
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struct mem_cgroup *memcg;
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};
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#define SHRINK_STOP (~0UL)
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#define SHRINK_EMPTY (~0UL - 1)
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/*
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* A callback you can register to apply pressure to ageable caches.
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*
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* @count_objects should return the number of freeable items in the cache. If
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* there are no objects to free, it should return SHRINK_EMPTY, while 0 is
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* returned in cases of the number of freeable items cannot be determined
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* or shrinker should skip this cache for this time (e.g., their number
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* is below shrinkable limit). No deadlock checks should be done during the
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* count callback - the shrinker relies on aggregating scan counts that couldn't
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* be executed due to potential deadlocks to be run at a later call when the
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* deadlock condition is no longer pending.
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*
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* @scan_objects will only be called if @count_objects returned a non-zero
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* value for the number of freeable objects. The callout should scan the cache
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* and attempt to free items from the cache. It should then return the number
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* of objects freed during the scan, or SHRINK_STOP if progress cannot be made
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* due to potential deadlocks. If SHRINK_STOP is returned, then no further
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* attempts to call the @scan_objects will be made from the current reclaim
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* context.
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*
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* @flags determine the shrinker abilities, like numa awareness
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*/
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struct shrinker {
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unsigned long (*count_objects)(struct shrinker *,
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struct shrink_control *sc);
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unsigned long (*scan_objects)(struct shrinker *,
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struct shrink_control *sc);
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long batch; /* reclaim batch size, 0 = default */
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int seeks; /* seeks to recreate an obj */
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unsigned flags;
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/*
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* The reference count of this shrinker. Registered shrinker have an
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* initial refcount of 1, then the lookup operations are now allowed
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* to use it via shrinker_try_get(). Later in the unregistration step,
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* the initial refcount will be discarded, and will free the shrinker
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* asynchronously via RCU after its refcount reaches 0.
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*/
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refcount_t refcount;
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struct completion done; /* use to wait for refcount to reach 0 */
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struct rcu_head rcu;
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void *private_data;
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/* These are for internal use */
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struct list_head list;
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#ifdef CONFIG_MEMCG
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/* ID in shrinker_idr */
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int id;
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#endif
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#ifdef CONFIG_SHRINKER_DEBUG
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int debugfs_id;
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const char *name;
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struct dentry *debugfs_entry;
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#endif
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/* objs pending delete, per node */
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atomic_long_t *nr_deferred;
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};
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#define DEFAULT_SEEKS 2 /* A good number if you don't know better. */
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/* Internal flags */
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#define SHRINKER_REGISTERED BIT(0)
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#define SHRINKER_ALLOCATED BIT(1)
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/* Flags for users to use */
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#define SHRINKER_NUMA_AWARE BIT(2)
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#define SHRINKER_MEMCG_AWARE BIT(3)
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/*
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* It just makes sense when the shrinker is also MEMCG_AWARE for now,
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* non-MEMCG_AWARE shrinker should not have this flag set.
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*/
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#define SHRINKER_NONSLAB BIT(4)
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__printf(2, 3)
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struct shrinker *shrinker_alloc(unsigned int flags, const char *fmt, ...);
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void shrinker_register(struct shrinker *shrinker);
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void shrinker_free(struct shrinker *shrinker);
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static inline bool shrinker_try_get(struct shrinker *shrinker)
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{
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return refcount_inc_not_zero(&shrinker->refcount);
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}
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static inline void shrinker_put(struct shrinker *shrinker)
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{
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if (refcount_dec_and_test(&shrinker->refcount))
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complete(&shrinker->done);
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}
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#ifdef CONFIG_SHRINKER_DEBUG
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extern int __printf(2, 3) shrinker_debugfs_rename(struct shrinker *shrinker,
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const char *fmt, ...);
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#else /* CONFIG_SHRINKER_DEBUG */
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static inline __printf(2, 3)
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int shrinker_debugfs_rename(struct shrinker *shrinker, const char *fmt, ...)
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{
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return 0;
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}
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#endif /* CONFIG_SHRINKER_DEBUG */
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#endif /* _LINUX_SHRINKER_H */
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