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0650b2b2 IR |
1 | /* SPDX-License-Identifier: GPL-2.0 */ |
2 | #ifndef PERF_SHARDED_MUTEX_H | |
3 | #define PERF_SHARDED_MUTEX_H | |
4 | ||
5 | #include "mutex.h" | |
6 | #include "hashmap.h" | |
7 | ||
8 | /* | |
9 | * In a situation where a lock is needed per object, having a mutex can be | |
10 | * relatively memory expensive (40 bytes on x86-64). If the object can be | |
11 | * constantly hashed, a sharded mutex is an alternative global pool of mutexes | |
12 | * where the mutex is looked up from a hash value. This can lead to collisions | |
13 | * if the number of shards isn't large enough. | |
14 | */ | |
15 | struct sharded_mutex { | |
16 | /* mutexes array is 1<<cap_bits in size. */ | |
17 | unsigned int cap_bits; | |
18 | struct mutex mutexes[]; | |
19 | }; | |
20 | ||
21 | struct sharded_mutex *sharded_mutex__new(size_t num_shards); | |
22 | void sharded_mutex__delete(struct sharded_mutex *sm); | |
23 | ||
24 | static inline struct mutex *sharded_mutex__get_mutex(struct sharded_mutex *sm, size_t hash) | |
25 | { | |
26 | return &sm->mutexes[hash_bits(hash, sm->cap_bits)]; | |
27 | } | |
28 | ||
29 | #endif /* PERF_SHARDED_MUTEX_H */ |