Re: [Qemu-devel] [PATCH 2/2] aio: improve aio_poll performance by checking epoll only once

[Stefan Hajnoczi <stefanha@redhat.com>]

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On Wed, Sep 14, 2016 at 07:03:39AM -0400, Yaowei Bai wrote:
> As epoll whether enabled or not is a global setting, we can just
> check it only once rather than checking it with every node iteration.
> Through this we can avoid a lot of checks when epoll is not enabled.
> 
> Signed-off-by: Yaowei Bai <baiyaowei@cmss.chinamobile.com>
> Reviewed-by: Xiubo Li <lixiubo@cmss.chinamobile.com>
> ---
>  aio-posix.c | 12 +++++++-----
>  1 file changed, 7 insertions(+), 5 deletions(-)

The commit message says "improve aio_poll performance" but no benchmark
results were provided.  Therefore I can't take this patch as a
performance optimization.  I'm still happy to merge the patch since it
makes the if statement simpler but I'll rename it to "aio-posix: avoid
unnecessary aio_epoll_enabled() calls".

I don't think this patch gives a measurable performance improvement.  If
you believe otherwise, please post benchmark results.  Please let me
know what you think.

Stefan

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