On Mon, Jul 23, 2018 at 7:23 PM, Daniel Borkmann <dan...@iogearbox.net> wrote: > > On 07/24/2018 04:15 AM, Neal Cardwell wrote: > > On Mon, Jul 23, 2018 at 8:49 PM Lawrence Brakmo <bra...@fb.com> wrote: > >> > >> We observed high 99 and 99.9% latencies when doing RPCs with DCTCP. The > >> problem is triggered when the last packet of a request arrives CE > >> marked. The reply will carry the ECE mark causing TCP to shrink its cwnd > >> to 1 (because there are no packets in flight). When the 1st packet of > >> the next request arrives, the ACK was sometimes delayed even though it > >> is CWR marked, adding up to 40ms to the RPC latency. > >> > >> This patch insures that CWR marked data packets arriving will be acked > >> immediately. > > ... > >> Modified based on comments by Neal Cardwell <ncardw...@google.com> > >> > >> Signed-off-by: Lawrence Brakmo <bra...@fb.com> > >> --- > >> net/ipv4/tcp_input.c | 9 ++++++++- > >> 1 file changed, 8 insertions(+), 1 deletion(-) > > > > Seems like a nice mechanism to have, IMHO. > > > > Acked-by: Neal Cardwell <ncardw...@google.com> > > Should this go to net tree instead where all the other fixes went? I am neutral but this feels more like a feature improvement
Acked-by: Yuchung Cheng <ych...@google.com> btw this should also help the classic ECN case upon timeout that triggers one packet retransmission. > > Thanks, > Daniel
