tools/perf/util/sharded_mutex.h

   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 */