[Cake] Query on ACK

[Dave Taht]

On Fri, May 8, 2020 at 8:08 AM Toke Høiland-Jørgensen <toke at redhat.com> wrote:
>
> Dave Taht <dave.taht at gmail.com> writes:
>
> > On Thu, May 7, 2020 at 11:36 PM Avakash bhat <avakash261 at gmail.com> wrote:
> >>
> >> Ok thanks so much for the clarifications.
> >> That cleared it up quite a bit.
> >
> > I note that there was something really subtle that could have been
> > done to improve cake's ack handling, and for all I know
> > it actually happened in the final codebase.
> >
> > so, please, go forth and duplicate the existing implementation, and
> > ignore me, cause looking at this hairy code gives me a
> > headache.
> >
> > anyway, to try and describe what I thought I saw an interaction with
> > the scheduler back in the day.
> >
> > The ack-filter runs, deleting all but one packet from the ack queue,
> > and delivers that.
> > the scheduler runs, serves a bunch of other flows, then returns to the
> > ack queue, which has accumulated a couple more packets,
> > the ack-filter runs, deleting all but one packet from the ack queue,
> > and delivers that, but doesn't exhaust its qauntum
>
> The ACK filter runs on enqueue, so if a queue has only ACKs in it, it
> will never accumulate anything in the first place...

but the side effect is that on dequeue, it flips it into the fast
queue drr rotation, not the slow, so it can't accumulate
as many acks before delivering the one it has left.

Or so I thought, way back when....

>
> -Toke
>


-- 
Make Music, Not War

Dave Täht
CTO, TekLibre, LLC
http://www.teklibre.com
Tel: 1-831-435-0729