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

[Yaowei Bai]

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 <address@hidden>
Reviewed-by: Xiubo Li <address@hidden>
---
 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