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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. |
7 | * |
8 | * The 'gfpmask' refers to the allocation we are currently trying to |
9 | * fulfil. |
10 | */ |
11 | struct shrink_control { |
12 | gfp_t gfp_mask; |
13 | |
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 | */ |
19 | unsigned long nr_to_scan; |
20 | |
21 | /* shrink from these nodes */ |
22 | nodemask_t nodes_to_scan; |
23 | /* current node being shrunk (for NUMA aware shrinkers) */ |
24 | int nid; |
25 | }; |
26 | |
27 | #define SHRINK_STOP (~0UL) |
28 | /* |
29 | * A callback you can register to apply pressure to ageable caches. |
30 | * |
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. |
37 | * |
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. |
45 | * |
46 | * @flags determine the shrinker abilities, like numa awareness |
47 | */ |
48 | struct shrinker { |
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 | |
54 | int seeks; /* seeks to recreate an obj */ |
55 | long batch; /* reclaim batch size, 0 = default */ |
56 | unsigned long flags; |
57 | |
58 | /* These are for internal use */ |
59 | struct list_head list; |
60 | /* objs pending delete, per node */ |
61 | atomic_long_t *nr_deferred; |
62 | }; |
63 | #define DEFAULT_SEEKS 2 /* A good number if you don't know better. */ |
64 | |
65 | /* Flags */ |
66 | #define SHRINKER_NUMA_AWARE (1 << 0) |
67 | |
68 | extern int register_shrinker(struct shrinker *); |
69 | extern void unregister_shrinker(struct shrinker *); |
70 | #endif |
71 |
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