Re: [PATCH net-next] tcp: ack immediately when a cwr packet arrives

2018-07-25 Thread David Miller
From: Neal Cardwell Date: Tue, 24 Jul 2018 21:57:27 -0400 > On Tue, Jul 24, 2018 at 1:42 PM Lawrence Brakmo wrote: >> >> Note that without this fix the 99% latencies when doing 10KB RPCs >> in a congested network using DCTCP are 40ms vs. 190us with the patch. >> Also note that these 40ms high

Re: [PATCH net-next] tcp: ack immediately when a cwr packet arrives

2018-07-24 Thread Neal Cardwell
On Tue, Jul 24, 2018 at 1:42 PM Lawrence Brakmo wrote: > > Note that without this fix the 99% latencies when doing 10KB RPCs > in a congested network using DCTCP are 40ms vs. 190us with the patch. > Also note that these 40ms high tail latencies started after commit >

Re: [PATCH net-next] tcp: ack immediately when a cwr packet arrives

2018-07-24 Thread Lawrence Brakmo
Note that without this fix the 99% latencies when doing 10KB RPCs in a congested network using DCTCP are 40ms vs. 190us with the patch. Also note that these 40ms high tail latencies started after commit 3759824da87b30ce7a35b4873b62b0ba38905ef5 in Jul 2015, which triggered the bugs/features we

Re: [PATCH net-next] tcp: ack immediately when a cwr packet arrives

2018-07-24 Thread Eric Dumazet
On 07/24/2018 10:12 AM, Neal Cardwell wrote: > On Tue, Jul 24, 2018 at 1:07 PM Yuchung Cheng wrote: >> >> On Mon, Jul 23, 2018 at 7:23 PM, Daniel Borkmann >> wrote: >>> Should this go to net tree instead where all the other fixes went? >> I am neutral but this feels more like a feature

Re: [PATCH net-next] tcp: ack immediately when a cwr packet arrives

2018-07-24 Thread Neal Cardwell
On Tue, Jul 24, 2018 at 1:07 PM Yuchung Cheng wrote: > > On Mon, Jul 23, 2018 at 7:23 PM, Daniel Borkmann wrote: > > Should this go to net tree instead where all the other fixes went? > I am neutral but this feels more like a feature improvement I agree this feels like a feature improvement

Re: [PATCH net-next] tcp: ack immediately when a cwr packet arrives

2018-07-24 Thread Yuchung Cheng
On Mon, Jul 23, 2018 at 7:23 PM, Daniel Borkmann wrote: > > On 07/24/2018 04:15 AM, Neal Cardwell wrote: > > On Mon, Jul 23, 2018 at 8:49 PM Lawrence Brakmo wrote: > >> > >> We observed high 99 and 99.9% latencies when doing RPCs with DCTCP. The > >> problem is triggered when the last packet of

Re: [PATCH net-next] tcp: ack immediately when a cwr packet arrives

2018-07-23 Thread Daniel Borkmann
On 07/24/2018 04:15 AM, Neal Cardwell wrote: > On Mon, Jul 23, 2018 at 8:49 PM Lawrence Brakmo 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

Re: [PATCH net-next] tcp: ack immediately when a cwr packet arrives

2018-07-23 Thread Neal Cardwell
On Mon, Jul 23, 2018 at 8:49 PM Lawrence Brakmo 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

[PATCH net-next] tcp: ack immediately when a cwr packet arrives

2018-07-23 Thread Lawrence Brakmo
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