30 lines
922 B
C
30 lines
922 B
C
/* 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 */
|