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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>
33 lines
684 B
C
33 lines
684 B
C
// SPDX-License-Identifier: GPL-2.0
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#include "sharded_mutex.h"
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#include <stdlib.h>
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struct sharded_mutex *sharded_mutex__new(size_t num_shards)
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{
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struct sharded_mutex *result;
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size_t size;
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unsigned int bits;
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for (bits = 0; ((size_t)1 << bits) < num_shards; bits++)
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;
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size = sizeof(*result) + sizeof(struct mutex) * (1 << bits);
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result = malloc(size);
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if (!result)
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return NULL;
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result->cap_bits = bits;
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for (size_t i = 0; i < ((size_t)1 << bits); i++)
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mutex_init(&result->mutexes[i]);
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return result;
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}
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void sharded_mutex__delete(struct sharded_mutex *sm)
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{
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for (size_t i = 0; i < ((size_t)1 << sm->cap_bits); i++)
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mutex_destroy(&sm->mutexes[i]);
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free(sm);
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}
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