RE: TCP reaching to maximum throughput after a long time

Machani, Yaniv
2016-04-13T20:26:41Z

On Wed, Apr 13, 2016 at 17:32:29, Neal Cardwell wrote:
> Miller; Eric Dumazet; Nandita Dukkipati; open list; Kama, Meirav
> Subject: Re: TCP reaching to maximum throughput after a long time
>
> I like the idea to disable hystart ack-train.
>
>
> Yaniv, can you please re-run your test with CUBIC in three different
> scenarios:
>
> a) echo 0 > /sys/module/tcp_cubic/parameters/hystart_detect
This fixes the issues, got to max throughput immediately.

>
> b) echo 1 > /sys/module/tcp_cubic/parameters/hystart_detect
>
This shows the same results as before, starting low and increasing slowly.

>
> c) echo 2 > /sys/module/tcp_cubic/parameters/hystart_detect
This gets us a bit higher at the beginning, but never (waited ~60 sec) goes to the max.

Appreciate your help on this.
Yaniv
>
>
> This should help us isolate whether the hystart ack-train algorithm is
> causing problems in this particular case.
>
> Thanks!
> neal
>
>
>
> On Tue, Apr 12, 2016 at 11:32 PM, Eric Dumazet
> <eric.dumazet@gmail.com>
> wrote:
>
>
> On Tue, 2016-04-12 at 20:08 -0700, Yuchung Cheng wrote:
>
> > based on the prev thread I propose we disable hystart ack-train. It
> is
> > brittle under various circumstances. We've disabled that at Google
> for
> > years.
>
> Right, but because we also use sch_fq packet scheduler and pacing ;)
>
>
>
>