From mboxrd@z Thu Jan  1 00:00:00 1970
Return-Path: <eric.dumazet@gmail.com>
Received: from mail-pa0-x22d.google.com (mail-pa0-x22d.google.com
	[IPv6:2607:f8b0:400e:c03::22d])
	(using TLSv1 with cipher RC4-SHA (128/128 bits))
	(Client CN "smtp.gmail.com",
	Issuer "Google Internet Authority" (verified OK))
	by huchra.bufferbloat.net (Postfix) with ESMTPS id 10E1D21F1D6
	for <codel@lists.bufferbloat.net>; Wed, 10 Jul 2013 16:07:20 -0700 (PDT)
Received: by mail-pa0-f45.google.com with SMTP id bi5so7154978pad.18
	for <codel@lists.bufferbloat.net>; Wed, 10 Jul 2013 16:07:19 -0700 (PDT)
DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20120113;
	h=message-id:subject:from:to:cc:date:in-reply-to:references
	:content-type:x-mailer:content-transfer-encoding:mime-version;
	bh=KjIE85S1i24QqBH506PA/pXKN4YvYjRkbAmB/sQrPTQ=;
	b=ap9ziYWwWdHUxuit6UhmWUniGU0kqTP7w+LrMWczLFA7Q7xFLuHy6yV4YMPl6hPWMZ
	+sCYvK4+61ocuTzvE/EucF+0MHls/YponFCevc2omHYazWvqgDK0s8ZeHrWfZUXanB+z
	jQAcDOGsECm+XbZ4jpQAOR4wo6MrN9HjKyf7zskIKn4h/HUz42s14YL1v82eVy6Amhtz
	QtNQBGDu2gh0EKgmt23qxAcNnOzqJIj45fhpPJ6W5GxAiRD7XitpUnkSUdDieZrLqZfW
	HyEdu4vCK8wCnl3kvATIIq0lsXvVB0zoe49Pu6ivSOpcVw8oNrDFaz83xeabgEun6du0
	DfaQ==
X-Received: by 10.66.149.40 with SMTP id tx8mr7500067pab.38.1373497639510;
	Wed, 10 Jul 2013 16:07:19 -0700 (PDT)
Received: from ?IPv6:2620:0:1000:3304:d49d:873e:bd9b:d524?
	([2620:0:1000:3304:d49d:873e:bd9b:d524])
	by mx.google.com with ESMTPSA id z14sm23002222pbt.0.2013.07.10.16.07.18
	for <multiple recipients>
	(version=SSLv3 cipher=RC4-SHA bits=128/128);
	Wed, 10 Jul 2013 16:07:19 -0700 (PDT)
Message-ID: <1373497638.4600.24.camel@edumazet-glaptop>
From: Eric Dumazet <eric.dumazet@gmail.com>
To: Dave Taht <dave.taht@gmail.com>
Date: Wed, 10 Jul 2013 16:07:18 -0700
In-Reply-To: <CAA93jw4JPqoTfNOzTRCKu_DJUMJsHzGZVe_GAaCq3hNYyTyOZw@mail.gmail.com>
References: <CAA93jw7+KqGS++yeC9oZikKX0c+U5OWH34hEOB-chNrQYyTLvw@mail.gmail.com>
	<CAMzhQmOZ=O6LkXh4GtOJok5PuspPEK2fFgg0pNqiAhiosk2pAA@mail.gmail.com>
	<CAGhGL2Auw0FuyondjZMgpe-87-3S6Mti2NYM04ML0LzaO+uRRA@mail.gmail.com>
	<CAMzhQmNDCXqWmFpo0gHU7tpxsH0VLS1HbKzkYUe=WvMNpva+xw@mail.gmail.com>
	<CAGhGL2Cx7h_0Mx=q9=ZzSN99qAvu-vOtgkQZm6=b3H=B5RJ7ww@mail.gmail.com>
	<EF9580F8-7CDF-4139-AD38-F53D43ED5F44@pollere.com>
	<CAA93jw4JPqoTfNOzTRCKu_DJUMJsHzGZVe_GAaCq3hNYyTyOZw@mail.gmail.com>
Content-Type: text/plain; charset="UTF-8"
X-Mailer: Evolution 3.2.3-0ubuntu6 
Content-Transfer-Encoding: 7bit
Mime-Version: 1.0
Cc: Keith Winstein <keithw@mit.edu>,
	"codel@lists.bufferbloat.net" <codel@lists.bufferbloat.net>
Subject: Re: [Codel] sprout
X-BeenThere: codel@lists.bufferbloat.net
X-Mailman-Version: 2.1.13
Precedence: list
List-Id: CoDel AQM discussions <codel.lists.bufferbloat.net>
List-Unsubscribe: <https://lists.bufferbloat.net/options/codel>,
	<mailto:codel-request@lists.bufferbloat.net?subject=unsubscribe>
List-Archive: <https://lists.bufferbloat.net/pipermail/codel>
List-Post: <mailto:codel@lists.bufferbloat.net>
List-Help: <mailto:codel-request@lists.bufferbloat.net?subject=help>
List-Subscribe: <https://lists.bufferbloat.net/listinfo/codel>,
	<mailto:codel-request@lists.bufferbloat.net?subject=subscribe>
X-List-Received-Date: Wed, 10 Jul 2013 23:07:20 -0000

On Wed, 2013-07-10 at 15:44 -0700, Dave Taht wrote:

> I'd made a suggestion elsewhere that TSQ migrate down in size from 128k to
> lower as the number of active flows increased. Something like
> tcp_limit_output_size = max((2*BQL's limit)/(number of flows),mtu)
> 
> but I realize now that tcp has no idea what interface it's going out
> at any given
> time... still I'm on a quest to minimize latency and let offloads still work..

At Google we tried to plug something at the time TX completion happens
(tcp_wfree())

The more time skb are waiting on qdisc, the less tcp_limit_output_size
should be for the TCP flow.

But tcp_limit_output_size had to be per socket tunable instead of
global. Experiments showed no real improvement over existing TCP
behavior.

The tcp_tso_should_defer() was kind of fixed lately [1] anyway, and we
plan to upstream another patch in this function to better preserve ACK
clocking.

[1] :
http://git.kernel.org/cgit/linux/kernel/git/davem/net-next.git/commit/?id=f4541d60a449afd40448b06496dcd510f505928e