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MDEV-5766 - my_atomic_load does memory writes

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my_atomic_load() is implemented as __sync_fetch_and_or(var, 0) which
writes or-ed value back to var. Memory writes as such have worse
performance and scalability than reads.

gcc 4.7 and up offers better facility for atomic loads/stores. Use it
whenever it is available.
This commit is contained in:
Sergey Vojtovich 2014-03-07 11:43:06 +04:00
parent 6dda6428d2
commit 9836fd5d13
1 changed files with 6 additions and 0 deletions
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6
include/atomic/gcc_builtins.h
View file

@ -31,6 +31,12 @@
#define make_atomic_store_body(S) *a= v
#define MY_ATOMIC_MODE "gcc-builtins-up"
#elif defined(__ATOMIC_SEQ_CST)
#define MY_ATOMIC_MODE "gcc-builtins-smp"
#define make_atomic_load_body(S) \
ret= __atomic_load_n(a, __ATOMIC_SEQ_CST)
#define make_atomic_store_body(S) \
__atomic_store_n(a, v, __ATOMIC_SEQ_CST)
#else
#define MY_ATOMIC_MODE "gcc-builtins-smp"
#define make_atomic_load_body(S) \