netdev - Re: [net-next] net: sched: pie: enable timestamp based delay calculation

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Message-ID: <CADAms0xNAj=hUhz6XmvM7kXBt0BNVb9EkaVdbgRkU_H_9je+_g@mail.gmail.com>
Date:   Thu, 29 Aug 2019 12:51:25 +0530
From:   Gautam Ramakrishnan <gautamramk@...il.com>
To:     Dave Taht <dave.taht@...il.com>
Cc:     Eric Dumazet <eric.dumazet@...il.com>,
        Linux Kernel Network Developers <netdev@...r.kernel.org>,
        Jamal Hadi Salim <jhs@...atatu.com>,
        "David S. Miller" <davem@...emloft.net>,
        Cong Wang <xiyou.wangcong@...il.com>,
        Leslie Monis <lesliemonis@...il.com>,
        "Mohit P . Tahiliani" <tahiliani@...k.edu.in>
Subject: Re: [net-next] net: sched: pie: enable timestamp based delay calculation

> > No module parameter is accepted these days.
> >
> > Please add a new attribute instead,
> > so that pie can be used in both mode on the same host.

We have prepared a new patch which sets the queue delay estimator as
an attribute instead of using module parameters

>
> I note that I think (but lack independent data) this improvement to
> the rate estimator in pie should improve its usability and accuracy
> in low rate or hw mq situations, and with some benchmarking to
> show the cpu impact (at high and low rates) of this improvement as
> well as the network
> impact, the old way should probably be dropped and new way adopted without
> needing a new variable to control it.
>
> A commit showing the before/after cpu and network impact with a whole
> bunch of flent benchmarks would be great.

We have tested for network impact using flent. However, we are unaware of
any standard methods to test for cpu impact. It would be helpful if
someone could suggest a method to test for cpu impact.
>
> (I'd also love to know if pie can be run with a lower target - like 5ms -
>  with this mod in place)

We will test it with target latencies of 5 and 10 ms as well.
>
> >
> > For a typical example of attribute addition, please take
> > a look at commit 48872c11b77271ef9b070bdc50afe6655c4eb9aa
> > ("net_sched: sch_fq: add dctcp-like marking")
>
> utilizing ce_threshold in this way is actually independent of whether or
> not you are using dctcp-style or rfc3168 style ecn marking.
>
> It's "I'm self congesting... Dooo something! Anything, to reduce the load!"
>
>
>
>
> --
>
> Dave Täht
> CTO, TekLibre, LLC
> http://www.teklibre.com
> Tel: 1-831-205-9740



-- 
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Gautam |