| Dave Chinner | b0d40c9 | 2011-07-08 14:14:42 +1000 | [diff] [blame] | 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. |
| 7 | */ |
| 8 | struct shrink_control { |
| 9 | gfp_t gfp_mask; |
| 10 | |
| 11 | /* How many slab objects shrinker() should scan and try to reclaim */ |
| 12 | unsigned long nr_to_scan; |
| 13 | }; |
| 14 | |
| 15 | /* |
| 16 | * A callback you can register to apply pressure to ageable caches. |
| 17 | * |
| 18 | * 'sc' is passed shrink_control which includes a count 'nr_to_scan' |
| 19 | * and a 'gfpmask'. It should look through the least-recently-used |
| 20 | * 'nr_to_scan' entries and attempt to free them up. It should return |
| 21 | * the number of objects which remain in the cache. If it returns -1, it means |
| 22 | * it cannot do any scanning at this time (eg. there is a risk of deadlock). |
| 23 | * |
| 24 | * The 'gfpmask' refers to the allocation we are currently trying to |
| 25 | * fulfil. |
| 26 | * |
| 27 | * Note that 'shrink' will be passed nr_to_scan == 0 when the VM is |
| 28 | * querying the cache size, so a fastpath for that case is appropriate. |
| 29 | */ |
| 30 | struct shrinker { |
| 31 | int (*shrink)(struct shrinker *, struct shrink_control *sc); |
| 32 | int seeks; /* seeks to recreate an obj */ |
| 33 | long batch; /* reclaim batch size, 0 = default */ |
| 34 | |
| 35 | /* These are for internal use */ |
| 36 | struct list_head list; |
| 37 | long nr; /* objs pending delete */ |
| 38 | }; |
| 39 | #define DEFAULT_SEEKS 2 /* A good number if you don't know better. */ |
| 40 | extern void register_shrinker(struct shrinker *); |
| 41 | extern void unregister_shrinker(struct shrinker *); |
| 42 | #endif |