[Cerowrt-devel] [Bloat] capacity awareness for the deadline scheduler

[Dave Taht]

On Mon, Jun 1, 2020 at 8:58 AM Michael Richardson <mcr at sandelman.ca> wrote:
>
>
> Dave Taht <dave.taht at gmail.com> wrote:
>     > Gradually, people seem to be getting more and more about basic queue theory.
>     > https://lwn.net/SubscriberLink/821578/ef5d913a20977921/
>
> Having skimmed the article, which seems to be mostly about CPU scheduling, I
> have a question.
>
> Does the availability of better *CPU* scheduling make it easier to do better
> TCP pacing?  Maybe that was your entire point?

It wasn't my entire point, it's just that I'm pleased to see more and
more progress in more people more deeply understanding kleinrocks
work.

as one example, pie's default rate estimator tends to go to hell in
the presence of jitter - be it induced by cpu scheduling, offloads,
pulling stuff off the rx ring, or putting it on the tx ring. A fixed
version of pie is documented here:
https://www.sciencedirect.com/science/article/abs/pii/S1389128619313775
. All I knew at the time pie was being developed was that it didn't
work well with hw multiqueue, I was not
aware the rate estimator problem was more general.

it worries me that pie is being naively applied to cable modem tech as
this problem does not show up in simple simulations.
>
> --
> ]               Never tell me the odds!                 | ipv6 mesh networks [
> ]   Michael Richardson, Sandelman Software Works        |    IoT architect   [
> ]     mcr at sandelman.ca  http://www.sandelman.ca/        |   ruby on rails    [
>


-- 
"For a successful technology, reality must take precedence over public
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dave at taht.net <Dave Täht> CTO, TekLibre, LLC Tel: 1-831-435-0729