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From: Oleksandr Natalenko <oleksandr@natalenko.name>
To: Eric Dumazet <edumazet@google.com>
Cc: "David S. Miller" <davem@davemloft.net>,
	Alexey Kuznetsov <kuznet@ms2.inr.ac.ru>,
	Hideaki YOSHIFUJI <yoshfuji@linux-ipv6.org>,
	netdev <netdev@vger.kernel.org>,
	LKML <linux-kernel@vger.kernel.org>,
	Soheil Hassas Yeganeh <soheil@google.com>,
	Neal Cardwell <ncardwell@google.com>,
	Yuchung Cheng <ycheng@google.com>, Van Jacobson <vanj@google.com>,
	Jerry Chu <hkchu@google.com>
Subject: Re: TCP and BBR: reproducibly low cwnd and bandwidth
Date: Fri, 16 Feb 2018 18:37:08 +0100	[thread overview]
Message-ID: <18081951.d6t0IUddpn@natalenko.name> (raw)
In-Reply-To: <CANn89iKqSkh=3D5-arubZkYdVTbb6C=OR5vK0sMDoO6S3A0GeQ@mail.gmail.com>

Hi.

On pátek 16. února 2018 17:25:58 CET Eric Dumazet wrote:
> The way TCP pacing works, it defaults to internal pacing using a hint
> stored in the socket.
> 
> If you change the qdisc while flow is alive, result could be unexpected.

I don't change a qdisc while flow is alive. Either the VM is completely 
restarted, or iperf3 is restarted on both sides.

> (TCP socket remembers that one FQ was supposed to handle the pacing)
> 
> What results do you have if you use standard pfifo_fast ?

Almost the same as with fq_codel (see my previous email with numbers).

> I am asking because TCP pacing relies on High resolution timers, and
> that might be weak on your VM.

Also, I've switched to measuring things on a real HW only (also see previous 
email with numbers).

Thanks.

Regards,
  Oleksandr

  reply	other threads:[~2018-02-16 17:37 UTC|newest]

Thread overview: 26+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-02-15 20:42 TCP and BBR: reproducibly low cwnd and bandwidth Oleksandr Natalenko
2018-02-16 15:15 ` Oleksandr Natalenko
2018-02-16 16:25   ` Eric Dumazet
2018-02-16 17:37     ` Oleksandr Natalenko [this message]
2018-02-16 16:26   ` Holger Hoffstätte
2018-02-16 16:56     ` Neal Cardwell
2018-02-16 17:13       ` Holger Hoffstätte
2018-02-16 17:35     ` Oleksandr Natalenko
2018-02-16 16:21 ` Eric Dumazet
     [not found]   ` <CADVnQymiswHBp32dcMvWd1WfYLpFqY4QTas8yABFQE7KKKc5ag@mail.gmail.com>
2018-02-16 16:43     ` Eric Dumazet
2018-02-16 16:45       ` Neal Cardwell
2018-02-16 17:00         ` Oleksandr Natalenko
2018-02-16 17:25     ` Oleksandr Natalenko
2018-02-16 17:56       ` Holger Hoffstätte
2018-02-16 19:54         ` Oleksandr Natalenko
2018-02-16 20:54       ` Eric Dumazet
2018-02-16 22:50         ` Eric Dumazet
2018-02-16 23:06           ` Oleksandr Natalenko
2018-02-16 22:50         ` Oleksandr Natalenko
2018-02-16 22:59           ` Eric Dumazet
2018-02-17 10:01             ` Oleksandr Natalenko
2018-02-17 18:52               ` Eric Dumazet
2018-02-18 21:04                 ` Eric Dumazet
2018-02-18 21:06                   ` Eric Dumazet
2018-02-18 21:49                   ` Oleksandr Natalenko
2018-02-18 22:24                     ` Eric Dumazet

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