Commit 31432412 authored May 23, 2005 by David S. Miller

[TCP]: Fix stretch ACK performance killer when doing ucopy.



When we are doing ucopy, we try to defer the ACK generation to
cleanup_rbuf().  This works most of the time very well, but if the
ucopy prequeue is large, this ACKing behavior kills performance.

With TSO, it is possible to fill the prequeue so large that by the
time the ACK is sent and gets back to the sender, most of the window
has emptied of data and performance suffers significantly.

This behavior does help in some cases, so we should think about
re-enabling this trick in the future, using some kind of limit in
order to avoid the bug case.

Signed-off-by: David S. Miller <davem@davemloft.net>

parent e16fa6b9

net/ipv4/tcp_input.c

+1 −10

Original line number	Diff line number	Diff line
		@@ -4355,16 +4355,7 @@ int tcp_rcv_established(struct sock sk, struct sk_buff skb,
		goto no_ack;
		}

		if (eaten) {
		if (tcp_in_quickack_mode(tp)) {
		tcp_send_ack(sk);
		} else {
		tcp_send_delayed_ack(sk);
		}
		} else {
		__tcp_ack_snd_check(sk, 0);
		}

		no_ack:
		if (eaten)
		__kfree_skb(skb);

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