63 lines
2.5 KiB
C
63 lines
2.5 KiB
C
#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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* Note that 'shrink' will be passed nr_to_scan == 0 when the VM is
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* querying the cache size, so a fastpath for that case is appropriate.
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*/
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struct shrink_control {
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gfp_t gfp_mask;
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/* How many slab objects shrinker() should scan and try to reclaim */
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unsigned long nr_to_scan;
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};
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#define SHRINK_STOP (~0UL)
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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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* @shrink() should look through the least-recently-used 'nr_to_scan' entries
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* and attempt to free them up. It should return the number of objects which
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* remain in the cache. If it returns -1, it means it cannot do any scanning at
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* this time (eg. there is a risk of deadlock).
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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 or the number of freeable items cannot be
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* determined, it should return 0. 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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struct shrinker {
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int (*shrink)(struct shrinker *, struct shrink_control *sc);
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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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/* These are for internal use */
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struct list_head list;
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atomic_long_t nr_in_batch; /* objs pending delete */
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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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extern void register_shrinker(struct shrinker *);
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extern void unregister_shrinker(struct shrinker *);
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#endif
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