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Kirill Tkhai
9b996468cf
We need to distinguish the situations when shrinker has very small amount of objects (see vfs_pressure_ratio() called from super_cache_count()), and when it has no objects at all. Currently, in the both of these cases, shrinker::count_objects() returns 0. The patch introduces new SHRINK_EMPTY return value, which will be used for "no objects at all" case. It's is a refactoring mostly, as SHRINK_EMPTY is replaced by 0 by all callers of do_shrink_slab() in this patch, and all the magic will happen in further. Link: http://lkml.kernel.org/r/153063069574.1818.11037751256699341813.stgit@localhost.localdomain Signed-off-by: Kirill Tkhai <[email protected]> Acked-by: Vladimir Davydov <[email protected]> Tested-by: Shakeel Butt <[email protected]> Cc: Al Viro <[email protected]> Cc: Andrey Ryabinin <[email protected]> Cc: Chris Wilson <[email protected]> Cc: Greg Kroah-Hartman <[email protected]> Cc: Guenter Roeck <[email protected]> Cc: "Huang, Ying" <[email protected]> Cc: Johannes Weiner <[email protected]> Cc: Josef Bacik <[email protected]> Cc: Li RongQing <[email protected]> Cc: Matthew Wilcox <[email protected]> Cc: Matthias Kaehlcke <[email protected]> Cc: Mel Gorman <[email protected]> Cc: Michal Hocko <[email protected]> Cc: Minchan Kim <[email protected]> Cc: Philippe Ombredanne <[email protected]> Cc: Roman Gushchin <[email protected]> Cc: Sahitya Tummala <[email protected]> Cc: Stephen Rothwell <[email protected]> Cc: Tetsuo Handa <[email protected]> Cc: Thomas Gleixner <[email protected]> Cc: Waiman Long <[email protected]> Signed-off-by: Andrew Morton <[email protected]> Signed-off-by: Linus Torvalds <[email protected]>
91 lines
3.1 KiB
C
91 lines
3.1 KiB
C
/* 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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/*
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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 extention 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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/*
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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 node being shrunk (for NUMA aware shrinkers) */
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int nid;
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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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int seeks; /* seeks to recreate an obj */
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long batch; /* reclaim batch size, 0 = default */
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unsigned long flags;
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/* These are for internal use */
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struct list_head list;
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#ifdef CONFIG_MEMCG_KMEM
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/* ID in shrinker_idr */
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int id;
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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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/* Flags */
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#define SHRINKER_NUMA_AWARE (1 << 0)
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#define SHRINKER_MEMCG_AWARE (1 << 1)
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extern int prealloc_shrinker(struct shrinker *shrinker);
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extern void register_shrinker_prepared(struct shrinker *shrinker);
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extern int register_shrinker(struct shrinker *shrinker);
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extern void unregister_shrinker(struct shrinker *shrinker);
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extern void free_prealloced_shrinker(struct shrinker *shrinker);
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#endif
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