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1/* SPDX-License-Identifier: GPL-2.0 */2#ifndef PERF_SHARDED_MUTEX_H3#define PERF_SHARDED_MUTEX_H4 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 be10 * relatively memory expensive (40 bytes on x86-64). If the object can be11 * constantly hashed, a sharded mutex is an alternative global pool of mutexes12 * where the mutex is looked up from a hash value. This can lead to collisions13 * if the number of shards isn't large enough.14 */15struct sharded_mutex {16 /* mutexes array is 1<<cap_bits in size. */17 unsigned int cap_bits;18 struct mutex mutexes[];19};20 21struct sharded_mutex *sharded_mutex__new(size_t num_shards);22void sharded_mutex__delete(struct sharded_mutex *sm);23 24static 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