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| author | Matt Stancliff <matt@genges.com> | 2014-06-26 08:52:53 -0400 |
|---|---|---|
| committer | Matt Stancliff <matt@genges.com> | 2014-06-26 08:52:53 -0400 |
| commit | a953c883815bada9365504940af52306d9a413ea (patch) | |
| tree | 8e2c06e446d2ef06dd8d27ecab92ecb900c3de8f /src/zmalloc.c | |
| parent | f9bca13a1a216c27509a6fb910f71c039dd60c7a (diff) | |
| download | redis-a953c883815bada9365504940af52306d9a413ea.tar.gz | |
Allow atomic memory count update with C11 builtins
From mailing list post https://groups.google.com/forum/#!topic/redis-db/QLjiQe4D7LA
In zmalloc.c the following primitives are currently used
to synchronize access to single global variable:
__sync_add_and_fetch
__sync_sub_and_fetch
In some architectures such as powerpc these primitives are overhead
intensive. More efficient C11 __atomic builtins are available with
newer GCC versions, see
http://gcc.gnu.org/onlinedocs/gcc-4.8.2/gcc/_005f_005fatomic-Builtins.html#_005f_005fatomic-Builtins
By substituting the following __atomic… builtins:
__atomic_add_fetch
__atomic_sub_fetch
the performance improvement on certain architectures such as powerpc can be significant,
around 10% to 15%, over the implementation using __sync builtins while there is only slight uptick on
Intel architectures because it was already enforcing Intel Strongly ordered memory semantics.
The selection of __atomic built-ins can be predicated on the definition of ATOMIC_RELAXED
which Is available on in gcc 4.8.2 and later versions.
Diffstat (limited to 'src/zmalloc.c')
| -rw-r--r-- | src/zmalloc.c | 7 |
1 files changed, 5 insertions, 2 deletions
diff --git a/src/zmalloc.c b/src/zmalloc.c index bd36654fb..11616e5ad 100644 --- a/src/zmalloc.c +++ b/src/zmalloc.c @@ -67,7 +67,10 @@ void zlibc_free(void *ptr) { #define free(ptr) je_free(ptr) #endif -#ifdef HAVE_ATOMIC +#if defined(__ATOMIC_RELAXED) +#define update_zmalloc_stat_add(__n) __atomic_add_fetch(&used_memory, (__n), __ATOMIC_RELAXED) +#define update_zmalloc_stat_sub(__n) __atomic_sub_fetch(&used_memory, (__n), __ATOMIC_RELAXED) +#elif defined(HAVE_ATOMIC) #define update_zmalloc_stat_add(__n) __sync_add_and_fetch(&used_memory, (__n)) #define update_zmalloc_stat_sub(__n) __sync_sub_and_fetch(&used_memory, (__n)) #else @@ -219,7 +222,7 @@ size_t zmalloc_used_memory(void) { size_t um; if (zmalloc_thread_safe) { -#ifdef HAVE_ATOMIC +#if defined(__ATOMIC_RELAXED) || defined(HAVE_ATOMIC) um = update_zmalloc_stat_add(0); #else pthread_mutex_lock(&used_memory_mutex); |