From mboxrd@z Thu Jan  1 00:00:00 1970
Return-Path: <eric.dumazet@gmail.com>
Received: from mail-bk0-f43.google.com (mail-bk0-f43.google.com
	[209.85.214.43]) (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 4C05D20228E;
	Wed, 16 May 2012 06:58:44 -0700 (PDT)
Received: by bkty5 with SMTP id y5so1362020bkt.16
	for <multiple recipients>; Wed, 16 May 2012 06:58:41 -0700 (PDT)
DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20120113;
	h=subject:from:to:cc:in-reply-to:references:content-type:date
	:message-id:mime-version:x-mailer:content-transfer-encoding;
	bh=x+65AHYicL+uMb2vHst8UMqXKLfnpOwMJoY847LoEwc=;
	b=ffjniLnw+PGWt6zd6rRve3saSOYm53xHmwdjc4u6Od65cI9GQhNhHllr5tgpPM9LOh
	aU2kchk2jff5qNaTfLijr5PbGMUMp1D/RRjUyQ1fS76TfxTKzVB2c1fJRtNnhL9bTJLt
	PQuexbLexJyDbFXyWqMqrhV2vCWCPLjiRx3OHxUVHxKr77Pn9ctqlwPu6PIXKKWTJukh
	dr6NFa+aOLFqvYfq/3fjZqG73Uyek83LYr5XpU4E+4tWgNemtQ6LHDHrl0eHS7qKfM1K
	kkDOpSjFlxCS80e4YgkDKAcEmnbLSsbD0OBWEVRaZAalSLfMsmp/nOZry5jovpE2QxV1
	h1IA==
Received: by 10.204.141.9 with SMTP id k9mr1122081bku.138.1337176721487;
	Wed, 16 May 2012 06:58:41 -0700 (PDT)
Received: from [172.28.91.41] ([74.125.122.49])
	by mx.google.com with ESMTPS id ie3sm5360781bkc.1.2012.05.16.06.58.39
	(version=SSLv3 cipher=OTHER); Wed, 16 May 2012 06:58:40 -0700 (PDT)
From: Eric Dumazet <eric.dumazet@gmail.com>
To: Dave Taht <dave.taht@gmail.com>
In-Reply-To: <1337156271.8512.1163.camel@edumazet-glaptop>
References: <CAA93jw7EUSf-NAg9q6oxRms5LQopO-VseYUtXAyCkUi=Yitx-g@mail.gmail.com>
	<4FA9FDC0.9010600@superduper.net>
	<CALw1_Q3iJ6o5du7GsO-VFObAyfett+Wuhq-pE_4Xaj1F+Vdw8A@mail.gmail.com>
	<B4D136A1-AF2D-4E98-91CC-D7098D040E91@gmail.com>
	<1337148560.8512.1123.camel@edumazet-glaptop>
	<4FB3519D.3020809@gmail.com>
	<CAA93jw5Yb+wSb0vCBrH6x+ED87z4qWi6t1OdZ6ws4KQhbOn25Q@mail.gmail.com>
	<1337154417.8512.1147.camel@edumazet-glaptop>
	<1337156271.8512.1163.camel@edumazet-glaptop>
Content-Type: text/plain; charset="UTF-8"
Date: Wed, 16 May 2012 15:58:23 +0200
Message-ID: <1337176703.8512.1181.camel@edumazet-glaptop>
Mime-Version: 1.0
X-Mailer: Evolution 2.28.3 
Content-Transfer-Encoding: 7bit
Cc: codel@lists.bufferbloat.net, bloat@lists.bufferbloat.net
Subject: Re: [Codel] [Bloat] Exploring the potential of codel, fq_codel,
	and qfq
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, 16 May 2012 13:58:46 -0000

On Wed, 2012-05-16 at 10:17 +0200, Eric Dumazet wrote:
> On Wed, 2012-05-16 at 09:47 +0200, Eric Dumazet wrote:
> 
> > On TCP_RR pure workload, you have one packet in flight per flow.
> > 
> > ECN adds nothing in this case, only that no 'drops' occurs at all.
> > 
> > It might be good to change fq_codel to perform ECN mark only if flow
> > queue has more packets.
> > 
> > If not, plain drop.
> 
> And for codel, if all packets are ECN enabled, there is no 'drop' on a
> pure TCP_RR workload, you endup codel downgraded to pfifo

Actually there is a bug in fq_codel :

The backlog used in codel_should_drop() should not be the flow backlog,
but qdisc backlog, since its more in the codel spirit (allowing a packet
to pass the congestion point regardless of its sojourn_time if the
current queue size is very small)

I'll send a patch to fix this.