Index: linux/net/ipv4//tcp_input.c
===================================================================
RCS file: /var/cvs/linux/net/ipv4/tcp_input.c,v
retrieving revision 1.1.1.10
diff -u -r1.1.1.10 tcp_input.c
--- linux/net/ipv4//tcp_input.c	1999/05/12 11:37:05	1.1.1.10
+++ linux/net/ipv4//tcp_input.c	1999/05/21 00:04:11
@@ -1585,7 +1585,9 @@
 	    /* We entered "quick ACK" mode or... */
 	    tcp_in_quickack_mode(tp) ||
 	    /* We have out of order data */
-	    (skb_peek(&tp->out_of_order_queue) != NULL)) {
+	    !skb_queue_empty(&tp->out_of_order_queue) ||
+	    /* TCP_NODELAY is set, this improves MPI performances. -Andrea */
+	    sk->nonagle == 1) {
 		/* Then ack it now */
 		tcp_send_ack(sk);
 	} else {