netdev - Re: TCP and BBR: reproducibly low cwnd and bandwidth

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Message-ID: <7131594.kGYvpCWkcy@natalenko.name>
Date:   Fri, 16 Feb 2018 20:54:47 +0100
From:   Oleksandr Natalenko <oleksandr@...alenko.name>
To:     Holger Hoffstätte 
        <holger@...lied-asynchrony.com>
Cc:     Neal Cardwell <ncardwell@...gle.com>,
        Eric Dumazet <eric.dumazet@...il.com>,
        "David S. Miller" <davem@...emloft.net>,
        Netdev <netdev@...r.kernel.org>,
        Yuchung Cheng <ycheng@...gle.com>,
        Soheil Hassas Yeganeh <soheil@...gle.com>,
        Jerry Chu <hkchu@...gle.com>,
        Eric Dumazet <edumazet@...gle.com>,
        Dave Taht <dave.taht@...il.com>
Subject: Re: TCP and BBR: reproducibly low cwnd and bandwidth

Hi.

On pátek 16. února 2018 18:56:12 CET Holger Hoffstätte wrote:
> There is simply no reason why you shouldn't get approx. line rate
> (~920+-ish) Mbit over wired 1GBit Ethernet; even my broken 10-year old
> Core2Duo laptop can do that. Can you boot with spectre_v2=off and try "the
> simplest case" with the defaults cubic/pfifo_fast? spectre_v2 has terrible
> performance impact esp. on small/older processors.

Just have tried. No visible difference.

> When I last benchmarked full PREEMPT with 4.9.x it was similarly bad and
> also had a noticeable network throughput impact even on my i7.
> 
> Also congratulations for being the only other person I know who ever tried
> YeAH. :-)

Well, according to the git log on tcp_yeah.c and Reported-by tag, I was not 
the only one there ;).

Regards,
  Oleksandr