netdev - Re: [PATCH v4 net-next 16/16] tcp_bbr: add BBR congestion control

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Message-ID: <CANn89iK=+FxFf7T27xymDmCTr-dwsjvCvwsaTYnM4GjTBn_cXA@mail.gmail.com>
Date:   Tue, 20 Sep 2016 16:56:28 -0700
From:   Eric Dumazet <edumazet@...gle.com>
To:     Neal Cardwell <ncardwell@...gle.com>
Cc:     Stephen Hemminger <stephen@...workplumber.org>,
        David Miller <davem@...emloft.net>,
        Netdev <netdev@...r.kernel.org>, Van Jacobson <vanj@...gle.com>,
        Yuchung Cheng <ycheng@...gle.com>,
        Nandita Dukkipati <nanditad@...gle.com>,
        Soheil Hassas Yeganeh <soheil@...gle.com>
Subject: Re: [PATCH v4 net-next 16/16] tcp_bbr: add BBR congestion control

On Tue, Sep 20, 2016 at 4:42 PM, Neal Cardwell <ncardwell@...gle.com> wrote:
>
> On Tue, Sep 20, 2016 at 7:39 PM, Stephen Hemminger
> <stephen@...workplumber.org> wrote:
> >
> >> NOTE: BBR *must* be used with the fq qdisc ("man tc-fq") with pacing
> >> enabled, since pacing is integral to the BBR design and
> >> implementation. BBR without pacing would not function properly, and
> >> may incur unnecessary high packet loss rates.
> >
> > Does it work with fq_codel?
>
> Good question. Since fq_codel does not (currently) implement pacing,
> it would not be sufficient to get the required behavior.
>
> neal


fq_codel is stochastic, so it wont work very well on hosts with
1,000,000 flows or more...

fq_codel is aimed for routers, while sch_fq targets hosts,
implementing pacing at a minimal cost (one high resolution timer per
qdisc)