1 /* SPDX-License-Identifier: GPL-2.0 */ 1 /* SPDX-License-Identifier: GPL-2.0 */
2 #ifndef _LINUX_SHRINKER_H 2 #ifndef _LINUX_SHRINKER_H
3 #define _LINUX_SHRINKER_H 3 #define _LINUX_SHRINKER_H
4 4
5 #include <linux/atomic.h> <<
6 #include <linux/types.h> <<
7 #include <linux/refcount.h> <<
8 #include <linux/completion.h> <<
9 <<
10 #define SHRINKER_UNIT_BITS BITS_PER_LONG <<
11 <<
12 /* <<
13 * Bitmap and deferred work of shrinker::id co <<
14 * shrinkers, which have elements charged to t <<
15 */ <<
16 struct shrinker_info_unit { <<
17 atomic_long_t nr_deferred[SHRINKER_UNI <<
18 DECLARE_BITMAP(map, SHRINKER_UNIT_BITS <<
19 }; <<
20 <<
21 struct shrinker_info { <<
22 struct rcu_head rcu; <<
23 int map_nr_max; <<
24 struct shrinker_info_unit *unit[]; <<
25 }; <<
26 <<
27 /* 5 /*
28 * This struct is used to pass information fro 6 * This struct is used to pass information from page reclaim to the shrinkers.
29 * We consolidate the values for easier extens !! 7 * We consolidate the values for easier extention later.
30 * 8 *
31 * The 'gfpmask' refers to the allocation we a 9 * The 'gfpmask' refers to the allocation we are currently trying to
32 * fulfil. 10 * fulfil.
33 */ 11 */
34 struct shrink_control { 12 struct shrink_control {
35 gfp_t gfp_mask; 13 gfp_t gfp_mask;
36 14
37 /* current node being shrunk (for NUMA 15 /* current node being shrunk (for NUMA aware shrinkers) */
38 int nid; 16 int nid;
39 17
40 /* 18 /*
41 * How many objects scan_objects shoul 19 * How many objects scan_objects should scan and try to reclaim.
42 * This is reset before every call, so 20 * This is reset before every call, so it is safe for callees
43 * to modify. 21 * to modify.
44 */ 22 */
45 unsigned long nr_to_scan; 23 unsigned long nr_to_scan;
46 24
47 /* 25 /*
48 * How many objects did scan_objects p 26 * How many objects did scan_objects process?
49 * This defaults to nr_to_scan before 27 * This defaults to nr_to_scan before every call, but the callee
50 * should track its actual progress. 28 * should track its actual progress.
51 */ 29 */
52 unsigned long nr_scanned; 30 unsigned long nr_scanned;
53 31
54 /* current memcg being shrunk (for mem 32 /* current memcg being shrunk (for memcg aware shrinkers) */
55 struct mem_cgroup *memcg; 33 struct mem_cgroup *memcg;
56 }; 34 };
57 35
58 #define SHRINK_STOP (~0UL) 36 #define SHRINK_STOP (~0UL)
59 #define SHRINK_EMPTY (~0UL - 1) 37 #define SHRINK_EMPTY (~0UL - 1)
60 /* 38 /*
61 * A callback you can register to apply pressu 39 * A callback you can register to apply pressure to ageable caches.
62 * 40 *
63 * @count_objects should return the number of 41 * @count_objects should return the number of freeable items in the cache. If
64 * there are no objects to free, it should ret 42 * there are no objects to free, it should return SHRINK_EMPTY, while 0 is
65 * returned in cases of the number of freeable 43 * returned in cases of the number of freeable items cannot be determined
66 * or shrinker should skip this cache for this 44 * or shrinker should skip this cache for this time (e.g., their number
67 * is below shrinkable limit). No deadlock che 45 * is below shrinkable limit). No deadlock checks should be done during the
68 * count callback - the shrinker relies on agg 46 * count callback - the shrinker relies on aggregating scan counts that couldn't
69 * be executed due to potential deadlocks to b 47 * be executed due to potential deadlocks to be run at a later call when the
70 * deadlock condition is no longer pending. 48 * deadlock condition is no longer pending.
71 * 49 *
72 * @scan_objects will only be called if @count 50 * @scan_objects will only be called if @count_objects returned a non-zero
73 * value for the number of freeable objects. T 51 * value for the number of freeable objects. The callout should scan the cache
74 * and attempt to free items from the cache. I 52 * and attempt to free items from the cache. It should then return the number
75 * of objects freed during the scan, or SHRINK 53 * of objects freed during the scan, or SHRINK_STOP if progress cannot be made
76 * due to potential deadlocks. If SHRINK_STOP 54 * due to potential deadlocks. If SHRINK_STOP is returned, then no further
77 * attempts to call the @scan_objects will be 55 * attempts to call the @scan_objects will be made from the current reclaim
78 * context. 56 * context.
79 * 57 *
80 * @flags determine the shrinker abilities, li 58 * @flags determine the shrinker abilities, like numa awareness
81 */ 59 */
82 struct shrinker { 60 struct shrinker {
83 unsigned long (*count_objects)(struct 61 unsigned long (*count_objects)(struct shrinker *,
84 struct 62 struct shrink_control *sc);
85 unsigned long (*scan_objects)(struct s 63 unsigned long (*scan_objects)(struct shrinker *,
86 struct s 64 struct shrink_control *sc);
87 65
88 long batch; /* reclaim batch size, 66 long batch; /* reclaim batch size, 0 = default */
89 int seeks; /* seeks to recreate a 67 int seeks; /* seeks to recreate an obj */
90 unsigned flags; 68 unsigned flags;
91 69
92 /* <<
93 * The reference count of this shrinke <<
94 * initial refcount of 1, then the loo <<
95 * to use it via shrinker_try_get(). L <<
96 * the initial refcount will be discar <<
97 * asynchronously via RCU after its re <<
98 */ <<
99 refcount_t refcount; <<
100 struct completion done; /* use to wait <<
101 struct rcu_head rcu; <<
102 <<
103 void *private_data; <<
104 <<
105 /* These are for internal use */ 70 /* These are for internal use */
106 struct list_head list; 71 struct list_head list;
107 #ifdef CONFIG_MEMCG 72 #ifdef CONFIG_MEMCG
108 /* ID in shrinker_idr */ 73 /* ID in shrinker_idr */
109 int id; 74 int id;
110 #endif 75 #endif
111 #ifdef CONFIG_SHRINKER_DEBUG <<
112 int debugfs_id; <<
113 const char *name; <<
114 struct dentry *debugfs_entry; <<
115 #endif <<
116 /* objs pending delete, per node */ 76 /* objs pending delete, per node */
117 atomic_long_t *nr_deferred; 77 atomic_long_t *nr_deferred;
118 }; 78 };
119 #define DEFAULT_SEEKS 2 /* A good number if yo 79 #define DEFAULT_SEEKS 2 /* A good number if you don't know better. */
120 80
121 /* Internal flags */ !! 81 /* Flags */
122 #define SHRINKER_REGISTERED BIT(0) !! 82 #define SHRINKER_NUMA_AWARE (1 << 0)
123 #define SHRINKER_ALLOCATED BIT(1) !! 83 #define SHRINKER_MEMCG_AWARE (1 << 1)
124 <<
125 /* Flags for users to use */ <<
126 #define SHRINKER_NUMA_AWARE BIT(2) <<
127 #define SHRINKER_MEMCG_AWARE BIT(3) <<
128 /* 84 /*
129 * It just makes sense when the shrinker is al 85 * It just makes sense when the shrinker is also MEMCG_AWARE for now,
130 * non-MEMCG_AWARE shrinker should not have th 86 * non-MEMCG_AWARE shrinker should not have this flag set.
131 */ 87 */
132 #define SHRINKER_NONSLAB BIT(4) !! 88 #define SHRINKER_NONSLAB (1 << 2)
133 89
134 __printf(2, 3) !! 90 extern int prealloc_shrinker(struct shrinker *shrinker);
135 struct shrinker *shrinker_alloc(unsigned int f !! 91 extern void register_shrinker_prepared(struct shrinker *shrinker);
136 void shrinker_register(struct shrinker *shrink !! 92 extern int register_shrinker(struct shrinker *shrinker);
137 void shrinker_free(struct shrinker *shrinker); !! 93 extern void unregister_shrinker(struct shrinker *shrinker);
138 !! 94 extern void free_prealloced_shrinker(struct shrinker *shrinker);
139 static inline bool shrinker_try_get(struct shr !! 95 #endif
140 { <<
141 return refcount_inc_not_zero(&shrinker <<
142 } <<
143 <<
144 static inline void shrinker_put(struct shrinke <<
145 { <<
146 if (refcount_dec_and_test(&shrinker->r <<
147 complete(&shrinker->done); <<
148 } <<
149 <<
150 #ifdef CONFIG_SHRINKER_DEBUG <<
151 extern int __printf(2, 3) shrinker_debugfs_ren <<
152 <<
153 #else /* CONFIG_SHRINKER_DEBUG */ <<
154 static inline __printf(2, 3) <<
155 int shrinker_debugfs_rename(struct shrinker *s <<
156 { <<
157 return 0; <<
158 } <<
159 #endif /* CONFIG_SHRINKER_DEBUG */ <<
160 #endif /* _LINUX_SHRINKER_H */ <<
161 96
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