[Cake] Large number of Flows

Dave Taht dave.taht at gmail.com
Mon Feb 17 09:34:29 EST 2020

fq_codel, Cake etc, supports an infinite number of flows.

It has a limited number of "queues" that can get mapped to flows, but
it's usually ok if a collision happens.

The 1024 queue tradeoff is based on the observation that usually a max
of a few hundred active flows exist, and furthermore,
excessive fair queueing tends to defeat the purpose of the aqm of
keeping overall flow lengths short. Collisions of two fat flows are

You can recompile cake with more queues if you like (fq_codel has a
soft limit of 64k queues). We don't have much data on 10GigE+
behaviors. It was kind
of my assumption more queues would help in the 40GigE world, but
that's usually got hardware mq (64 or more), and what I'm seeing there
is 64 default fq_codel instances, 64k
queues essentially, and I think that's WAY too much....

On Mon, Feb 17, 2020 at 6:07 AM Mike <mike at surfglobal.net> wrote:
> Will cake support a large number of flows like over a thousand per linux box without any modifications.  I did see that there was a qdisc issue for fq_codel on a large scale.  We would be using linux kernel 4.19 which has cake already in it.  Any help or issues that might be encountered in scaling would be appreciated.
> Thanks
> Mike Thompson
> _______________________________________________
> Cake mailing list
> Cake at lists.bufferbloat.net
> https://lists.bufferbloat.net/listinfo/cake

Make Music, Not War

Dave Täht
CTO, TekLibre, LLC
Tel: 1-831-435-0729

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