Re: [Qemu-block] [PATCH 2/2] aio: improve aio_poll performance by checking epoll only once
On Wed, Sep 14, 2016 at 05:40:17PM +0100, Stefan Hajnoczi wrote: > 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 > > Reviewed-by: Xiubo Li > > --- > > 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". Sorry for replying late, i just came back from my vacation. And i'd like to say it's ok for me to rename the commit message. Thank you for doing it. > > I don't think this patch gives a measurable performance improvement. If Yes, i agree with you at this point in consideration of there's no too many fds to poll at most time. > you believe otherwise, please post benchmark results. Please let me > know what you think. > > Stefan
Re: [Qemu-block] [PATCH 2/2] aio: improve aio_poll performance by checking epoll only once
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 > Reviewed-by: Xiubo Li > --- > 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 signature.asc Description: PGP signature
[Qemu-block] [PATCH 2/2] aio: improve aio_poll performance by checking epoll only once
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
Reviewed-by: Xiubo Li
---
aio-posix.c | 12 +++-
1 file changed, 7 insertions(+), 5 deletions(-)
diff --git a/aio-posix.c b/aio-posix.c
index 43162a9..4ef34dd 100644
--- a/aio-posix.c
+++ b/aio-posix.c
@@ -431,11 +431,13 @@ bool aio_poll(AioContext *ctx, bool blocking)
assert(npfd == 0);
/* fill pollfds */
-QLIST_FOREACH(node, &ctx->aio_handlers, node) {
-if (!node->deleted && node->pfd.events
-&& !aio_epoll_enabled(ctx)
-&& aio_node_check(ctx, node->is_external)) {
-add_pollfd(node);
+
+if (!aio_epoll_enabled(ctx)) {
+QLIST_FOREACH(node, &ctx->aio_handlers, node) {
+if (!node->deleted && node->pfd.events
+&& aio_node_check(ctx, node->is_external)) {
+add_pollfd(node);
+}
}
}
--
1.8.3.1
