1234567891011121314151617181920212223242526272829303132333435363738394041424344454647484950515253545556575859606162636465 |
- #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.
- *
- * Note that 'shrink' will be passed nr_to_scan == 0 when the VM is
- * querying the cache size, so a fastpath for that case is appropriate.
- */
- struct shrink_control {
- gfp_t gfp_mask;
- /* How many slab objects shrinker() should scan and try to reclaim */
- unsigned long nr_to_scan;
- /* shrink from these nodes */
- nodemask_t nodes_to_scan;
- };
- #define SHRINK_STOP (~0UL)
- /*
- * A callback you can register to apply pressure to ageable caches.
- *
- * @shrink() should look through the least-recently-used 'nr_to_scan' entries
- * and attempt to free them up. It should return the number of objects which
- * remain in the cache. If it returns -1, it means it cannot do any scanning at
- * this time (eg. there is a risk of deadlock).
- *
- * @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.
- */
- struct shrinker {
- int (*shrink)(struct shrinker *, struct shrink_control *sc);
- 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 */
- /* These are for internal use */
- struct list_head list;
- atomic_long_t nr_in_batch; /* objs pending delete */
- };
- #define DEFAULT_SEEKS 2 /* A good number if you don't know better. */
- extern void register_shrinker(struct shrinker *);
- extern void unregister_shrinker(struct shrinker *);
- #endif
|