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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. | |
b0d40c92 DC |
10 | */ |
11 | struct shrink_control { | |
12 | gfp_t gfp_mask; | |
13 | ||
a0b02131 DC |
14 | /* |
15 | * How many objects scan_objects should scan and try to reclaim. | |
16 | * This is reset before every call, so it is safe for callees | |
17 | * to modify. | |
18 | */ | |
b0d40c92 | 19 | unsigned long nr_to_scan; |
0ce3d744 DC |
20 | |
21 | /* shrink from these nodes */ | |
22 | nodemask_t nodes_to_scan; | |
1d3d4437 GC |
23 | /* current node being shrunk (for NUMA aware shrinkers) */ |
24 | int nid; | |
b0d40c92 DC |
25 | }; |
26 | ||
24f7c6b9 | 27 | #define SHRINK_STOP (~0UL) |
b0d40c92 DC |
28 | /* |
29 | * A callback you can register to apply pressure to ageable caches. | |
30 | * | |
24f7c6b9 DC |
31 | * @count_objects should return the number of freeable items in the cache. If |
32 | * there are no objects to free or the number of freeable items cannot be | |
33 | * determined, it should return 0. No deadlock checks should be done during the | |
34 | * count callback - the shrinker relies on aggregating scan counts that couldn't | |
35 | * be executed due to potential deadlocks to be run at a later call when the | |
36 | * deadlock condition is no longer pending. | |
b0d40c92 | 37 | * |
24f7c6b9 DC |
38 | * @scan_objects will only be called if @count_objects returned a non-zero |
39 | * value for the number of freeable objects. The callout should scan the cache | |
40 | * and attempt to free items from the cache. It should then return the number | |
41 | * of objects freed during the scan, or SHRINK_STOP if progress cannot be made | |
42 | * due to potential deadlocks. If SHRINK_STOP is returned, then no further | |
43 | * attempts to call the @scan_objects will be made from the current reclaim | |
44 | * context. | |
1d3d4437 GC |
45 | * |
46 | * @flags determine the shrinker abilities, like numa awareness | |
b0d40c92 DC |
47 | */ |
48 | struct shrinker { | |
24f7c6b9 DC |
49 | unsigned long (*count_objects)(struct shrinker *, |
50 | struct shrink_control *sc); | |
51 | unsigned long (*scan_objects)(struct shrinker *, | |
52 | struct shrink_control *sc); | |
53 | ||
b0d40c92 DC |
54 | int seeks; /* seeks to recreate an obj */ |
55 | long batch; /* reclaim batch size, 0 = default */ | |
1d3d4437 | 56 | unsigned long flags; |
b0d40c92 DC |
57 | |
58 | /* These are for internal use */ | |
59 | struct list_head list; | |
1d3d4437 GC |
60 | /* objs pending delete, per node */ |
61 | atomic_long_t *nr_deferred; | |
b0d40c92 DC |
62 | }; |
63 | #define DEFAULT_SEEKS 2 /* A good number if you don't know better. */ | |
1d3d4437 GC |
64 | |
65 | /* Flags */ | |
66 | #define SHRINKER_NUMA_AWARE (1 << 0) | |
67 | ||
68 | extern int register_shrinker(struct shrinker *); | |
b0d40c92 DC |
69 | extern void unregister_shrinker(struct shrinker *); |
70 | #endif |