On 2018-11-05 22:51, Honnappa Nagarahalli wrote:
I've also run an out-of-tree DSW throughput benchmark, and I've found that
going from Non-C11 to C11 gives a 4% slowdown. After this patch, the
slowdown is only 2,8%.
This is interesting. The general understanding seems to be that C11 atomics
should not add any additional instructions on x86. But, we still see some drop
in performance. Is this attributed to compiler not being allowed to re-order?
I was lazy enough not to disassemble, so I don't know.
I would suggest non-C11 mode stays as the default on x86_64.
