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 */ |
30 | |