OPTIM: stream_sock: save a failed recv syscall when splice returns EAGAIN
When splice() returns EAGAIN, on old kernels it could be caused by a read
shutdown which was not detected. Due to this behaviour, we had to fall
back to recv(), which in turn says if it's a real EAGAIN or a shutdown.
Since this behaviour was fixed in 2.6.27.14, on more recent kernels we'd
prefer to avoid the fallback to recv() when possible. For this, we set a
variable the first time splice() detects a shutdown, to indicate that it
works. We can then rely on this variable to adjust our behaviour.
Doing this alone increased the overall performance by about 1% on medium
sized objects.
diff --git a/src/stream_sock.c b/src/stream_sock.c
index c41c652..29b7fcb 100644
--- a/src/stream_sock.c
+++ b/src/stream_sock.c
@@ -73,6 +73,7 @@
*/
static int stream_sock_splice_in(struct buffer *b, struct stream_interface *si)
{
+ static int splice_detects_close;
int fd = si->fd;
int ret;
unsigned long max;
@@ -128,8 +129,10 @@
if (ret <= 0) {
if (ret == 0) {
/* connection closed. This is only detected by
- * recent kernels (>= 2.6.27.13).
+ * recent kernels (>= 2.6.27.13). If we notice
+ * it works, we store the info for later use.
*/
+ splice_detects_close = 1;
b->flags |= BF_READ_NULL;
retval = 1; /* no need for further polling */
break;
@@ -151,13 +154,18 @@
break;
}
- /* We don't know if the connection was closed.
+ /* We don't know if the connection was closed,
+ * but if we know splice detects close, then we
+ * know it for sure.
* But if we're called upon POLLIN with an empty
- * pipe and get EAGAIN, it is suspect enought to
+ * pipe and get EAGAIN, it is suspect enough to
* try to fall back to the normal recv scheme
* which will be able to deal with the situation.
*/
- retval = -1;
+ if (splice_detects_close)
+ retval = 0; /* we know for sure that it's EAGAIN */
+ else
+ retval = -1;
break;
}