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/* SPDX-License-Identifier: GPL-2.0 */
#ifndef PERF_SHARDED_MUTEX_H
#define PERF_SHARDED_MUTEX_H
#include "mutex.h"
#include "hashmap.h"
/*
* In a situation where a lock is needed per object, having a mutex can be
* relatively memory expensive (40 bytes on x86-64). If the object can be
* constantly hashed, a sharded mutex is an alternative global pool of mutexes
* where the mutex is looked up from a hash value. This can lead to collisions
* if the number of shards isn't large enough.
*/
struct sharded_mutex {
/* mutexes array is 1<<cap_bits in size. */
unsigned int cap_bits;
struct mutex mutexes[];
};
struct sharded_mutex *sharded_mutex__new(size_t num_shards);
void sharded_mutex__delete(struct sharded_mutex *sm);
static inline struct mutex *sharded_mutex__get_mutex(struct sharded_mutex *sm, size_t hash)
{
return &sm->mutexes[hash_bits(hash, sm->cap_bits)];
}
#endif /* PERF_SHARDED_MUTEX_H */
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