mirror of
https://github.com/torvalds/linux.git
synced 2025-11-04 10:40:15 +02:00
0650b2b2e6
Per object mutexes may come with significant memory cost while a
global mutex can suffer from unnecessary contention. A sharded mutex
is a compromise where objects are hashed and then a particular mutex
for the hash of the object used. Contention can be controlled by the
number of shards.
v2. Use hashmap.h's hash_bits in case of contention from alignment of
objects.
Signed-off-by: Ian Rogers <irogers@google.com>
Acked-by: Namhyung Kim <namhyung@kernel.org>
Cc: Andres Freund <andres@anarazel.de>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Yuan Can <yuancan@huawei.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Arnaldo Carvalho de Melo <acme@kernel.org>
Cc: Huacai Chen <chenhuacai@kernel.org>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Masami Hiramatsu <mhiramat@kernel.org>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Kan Liang <kan.liang@linux.intel.com>
Cc: Ingo Molnar <mingo@redhat.com>
Link: https://lore.kernel.org/r/20230615040715.2064350-1-irogers@google.com
Signed-off-by: Namhyung Kim <namhyung@kernel.org>
29 lines
922 B
C
29 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 */
|