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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. | |
24f7c6b9 DC |
7 | * |
8 | * The 'gfpmask' refers to the allocation we are currently trying to | |
9 | * fulfil. | |
10 | * | |
11 | * Note that 'shrink' will be passed nr_to_scan == 0 when the VM is | |
12 | * querying the cache size, so a fastpath for that case is appropriate. | |
b0d40c92 DC |
13 | */ |
14 | struct shrink_control { | |
15 | gfp_t gfp_mask; | |
16 | ||
17 | /* How many slab objects shrinker() should scan and try to reclaim */ | |
18 | unsigned long nr_to_scan; | |
0ce3d744 DC |
19 | |
20 | /* shrink from these nodes */ | |
21 | nodemask_t nodes_to_scan; | |
b0d40c92 DC |
22 | }; |
23 | ||
24f7c6b9 | 24 | #define SHRINK_STOP (~0UL) |
b0d40c92 DC |
25 | /* |
26 | * A callback you can register to apply pressure to ageable caches. | |
27 | * | |
24f7c6b9 DC |
28 | * @shrink() should look through the least-recently-used 'nr_to_scan' entries |
29 | * and attempt to free them up. It should return the number of objects which | |
30 | * remain in the cache. If it returns -1, it means it cannot do any scanning at | |
31 | * this time (eg. there is a risk of deadlock). | |
b0d40c92 | 32 | * |
24f7c6b9 DC |
33 | * @count_objects should return the number of freeable items in the cache. If |
34 | * there are no objects to free or the number of freeable items cannot be | |
35 | * determined, it should return 0. No deadlock checks should be done during the | |
36 | * count callback - the shrinker relies on aggregating scan counts that couldn't | |
37 | * be executed due to potential deadlocks to be run at a later call when the | |
38 | * deadlock condition is no longer pending. | |
b0d40c92 | 39 | * |
24f7c6b9 DC |
40 | * @scan_objects will only be called if @count_objects returned a non-zero |
41 | * value for the number of freeable objects. The callout should scan the cache | |
42 | * and attempt to free items from the cache. It should then return the number | |
43 | * of objects freed during the scan, or SHRINK_STOP if progress cannot be made | |
44 | * due to potential deadlocks. If SHRINK_STOP is returned, then no further | |
45 | * attempts to call the @scan_objects will be made from the current reclaim | |
46 | * context. | |
b0d40c92 DC |
47 | */ |
48 | struct shrinker { | |
49 | int (*shrink)(struct shrinker *, struct shrink_control *sc); | |
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50 | unsigned long (*count_objects)(struct shrinker *, |
51 | struct shrink_control *sc); | |
52 | unsigned long (*scan_objects)(struct shrinker *, | |
53 | struct shrink_control *sc); | |
54 | ||
b0d40c92 DC |
55 | int seeks; /* seeks to recreate an obj */ |
56 | long batch; /* reclaim batch size, 0 = default */ | |
57 | ||
58 | /* These are for internal use */ | |
59 | struct list_head list; | |
83aeeada | 60 | atomic_long_t nr_in_batch; /* objs pending delete */ |
b0d40c92 DC |
61 | }; |
62 | #define DEFAULT_SEEKS 2 /* A good number if you don't know better. */ | |
63 | extern void register_shrinker(struct shrinker *); | |
64 | extern void unregister_shrinker(struct shrinker *); | |
65 | #endif |