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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. | |
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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. | |
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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; | |
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19 | |
20 | /* shrink from these nodes */ | |
21 | nodemask_t nodes_to_scan; | |
1d3d4437 GC |
22 | /* current node being shrunk (for NUMA aware shrinkers) */ |
23 | int nid; | |
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24 | }; |
25 | ||
24f7c6b9 | 26 | #define SHRINK_STOP (~0UL) |
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27 | /* |
28 | * A callback you can register to apply pressure to ageable caches. | |
29 | * | |
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30 | * @shrink() should look through the least-recently-used 'nr_to_scan' entries |
31 | * and attempt to free them up. It should return the number of objects which | |
32 | * remain in the cache. If it returns -1, it means it cannot do any scanning at | |
33 | * this time (eg. there is a risk of deadlock). | |
b0d40c92 | 34 | * |
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35 | * @count_objects should return the number of freeable items in the cache. If |
36 | * there are no objects to free or the number of freeable items cannot be | |
37 | * determined, it should return 0. No deadlock checks should be done during the | |
38 | * count callback - the shrinker relies on aggregating scan counts that couldn't | |
39 | * be executed due to potential deadlocks to be run at a later call when the | |
40 | * deadlock condition is no longer pending. | |
b0d40c92 | 41 | * |
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42 | * @scan_objects will only be called if @count_objects returned a non-zero |
43 | * value for the number of freeable objects. The callout should scan the cache | |
44 | * and attempt to free items from the cache. It should then return the number | |
45 | * of objects freed during the scan, or SHRINK_STOP if progress cannot be made | |
46 | * due to potential deadlocks. If SHRINK_STOP is returned, then no further | |
47 | * attempts to call the @scan_objects will be made from the current reclaim | |
48 | * context. | |
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49 | * |
50 | * @flags determine the shrinker abilities, like numa awareness | |
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51 | */ |
52 | struct shrinker { | |
53 | int (*shrink)(struct shrinker *, struct shrink_control *sc); | |
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54 | unsigned long (*count_objects)(struct shrinker *, |
55 | struct shrink_control *sc); | |
56 | unsigned long (*scan_objects)(struct shrinker *, | |
57 | struct shrink_control *sc); | |
58 | ||
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59 | int seeks; /* seeks to recreate an obj */ |
60 | long batch; /* reclaim batch size, 0 = default */ | |
1d3d4437 | 61 | unsigned long flags; |
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62 | |
63 | /* These are for internal use */ | |
64 | struct list_head list; | |
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65 | /* objs pending delete, per node */ |
66 | atomic_long_t *nr_deferred; | |
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67 | }; |
68 | #define DEFAULT_SEEKS 2 /* A good number if you don't know better. */ | |
1d3d4437 GC |
69 | |
70 | /* Flags */ | |
71 | #define SHRINKER_NUMA_AWARE (1 << 0) | |
72 | ||
73 | extern int register_shrinker(struct shrinker *); | |
b0d40c92 DC |
74 | extern void unregister_shrinker(struct shrinker *); |
75 | #endif |