Re: TCP reaching to maximum throughput after a long time

Eric Dumazet
2016-04-12T20:17:39Z

On Tue, 2016-04-12 at 13:11 -0700, Ben Greear wrote:
> On 04/12/2016 12:31 PM, Machani, Yaniv wrote:
> > On Tue, Apr 12, 2016 at 18:04:52, Ben Greear wrote:
> >> On 04/12/2016 07:52 AM, Eric Dumazet wrote:
> >>> On Tue, 2016-04-12 at 12:17 +0000, Machani, Yaniv wrote:
> >>>>
> >>
> >> If you are using 'Cubic' TCP congestion control, then please try
> >> something different.
> >> It was broken last I checked, at least when used with the ath10k driver.
> >>
> >
> > Thanks Ben, this indeed seems to be the issue !
> > Switching to reno got me to max throughput instantly.
> >
> > I'm still looking through the thread you have shared, but from what I understand there is no planned fix for it ?
>
> I think at the time it was blamed on ath10k and no one cared to try to fix it.
>
> Or, maybe no one really uses CUBIC anymore?
>
> Either way, I have no plans to try to fix CUBIC, but maybe someone who knows
> this code better could give it a try.

Well, cubic seems to work in many cases, assuming they are not too many
drops.

Assuming one flow can get nominal speed in few RTT is kind a dream, and
so far nobody claimed a CC was able to do that, while still being fair
and resilient.

TCP CC are full of heuristics, and by definition heuristics that were
working 6 years ago might need to be refreshed.

We are still maintaining Cubic for sure.