On Sun, 2012-08-05 at 20:40 +0200, Eric Dumazet wrote: > On Sun, 2012-08-05 at 11:14 -0700, Yuchung Cheng wrote: > > On Sun, Aug 5, 2012 at 10:35 AM, Eric Dumazet <eric.duma...@gmail.com> > > wrote: > > > On Sun, 2012-08-05 at 19:26 +0200, Eric Dumazet wrote: > > > > > >> It could be a flaw in linux implementation, I admit we had so many bugs > > >> that it could very well be still buggy. > > > > > > And at first glance, the following tcpdump seems suspect : We can see > > > all ACK are delayed by about 40 ms > > but RFC 3168 (sec 6.1.3) does not mandate immediate ACKs for ECE > > marked ones? is this because ECN response is per round-trip? > > > > We should IMHO not delay ACKS, exactly like we react to a dropped > packet. > > If not specified in RFC 3168, it seems a forgotten point.
Following patch does the trick. Delaying ACK while sender might have a cwnd = 1 is not nice at all. I get better behavior, but still codel with Dave patch (mark all packets if above 'target') is giving an unfair advantage to non ECN flow. diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c index 2fd2bc9..b03f429 100644 --- a/net/ipv4/tcp_input.c +++ b/net/ipv4/tcp_input.c @@ -237,6 +237,7 @@ static inline void TCP_ECN_check_ce(struct tcp_sock *tp, const struct sk_buff *s tcp_enter_quickack_mode((struct sock *)tp); break; case INET_ECN_CE: + inet_csk((struct sock *)tp)->icsk_ack.quick |= 1; tp->ecn_flags |= TCP_ECN_DEMAND_CWR; /* fallinto */ default: _______________________________________________ Codel mailing list Codel@lists.bufferbloat.net https://lists.bufferbloat.net/listinfo/codel