nbd: set TCP_NODELAY

Disable the Nagle algorithm to reduce latency.  Note this means we must
also use TCP_CORK when sending header followed by payload to avoid
fragmenting lots of little packets.  The previous patch took care of
that.

Suggested-by: Nick Thomas <nick@bytemark.co.uk>
Tested-by: Nick Thomas <nick@bytemark.co.uk>
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

diff --git a/block/nbd.c b/block/nbd.c
index 485bbf0b8162c6bacd05cf392c40a0d4fce617e6..d9dc454498a0618e8cb0c55ac13c115b4226b3ae 100644 (file)
--- a/block/nbd.c
+++ b/block/nbd.c
@@ -406,6 +406,9 @@ static int nbd_establish_connection(BlockDriverState *bs)
         sock = unix_socket_outgoing(qemu_opt_get(s->socket_opts, "path"));
     } else {
         sock = tcp_socket_outgoing_opts(s->socket_opts);
+        if (sock >= 0) {
+            socket_set_nodelay(sock);
+        }
     }
 
     /* Failed to establish connection */