From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: 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 2DEBE2021A8 for ; Mon, 6 Aug 2012 13:01:14 -0700 (PDT) Received: by bkty15 with SMTP id y15so2007983bkt.16 for ; Mon, 06 Aug 2012 13:01:12 -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=KipF2KUDwIXclGf0RB7+N4Z3fkF29VH48rlzQkRqX2g=; b=hISiz/443+s3+wOrpokG8KFa4YqLyI6wW+m58DpAwNKy6Zest70EgFqIBHmyF/Qjqf PM+mS10kfayuI6AXysQhf/Xuf0+rWnaa313S+PTakalWqKniDiosV+x3sSQ/OTiTHkfN IEZJu11a9o6EUM1IxY4djQu/DWzM1EvpPNlUcaW4Ifpp5pdiETT9Ht1zZVHmNab1JfeJ hoV9YNygqs6wKd/OU5RXoThGBFJuD9B7NGthkAHpfSl4K87M9kFtc/yNBYpmCPFJE1zt 4ciilTUuwkA1hvvsz1dDGDSfFDJDlZBAc2ZbPbKtJrhnk2RoQ13UKlPvBwAgUv5beleg XJqA== Received: by 10.205.118.138 with SMTP id fq10mr4802989bkc.58.1344283272821; Mon, 06 Aug 2012 13:01:12 -0700 (PDT) Received: from [172.28.91.36] ([74.125.122.49]) by mx.google.com with ESMTPS id ht18sm7939680bkc.16.2012.08.06.13.01.10 (version=SSLv3 cipher=OTHER); Mon, 06 Aug 2012 13:01:11 -0700 (PDT) From: Eric Dumazet To: Andrew McGregor In-Reply-To: <441D6067-BC04-4461-BD91-4A988A089866@gmail.com> References: <1344048299-26267-1-git-send-email-dave.taht@bufferbloat.net> <1344062738.9299.1453.camel@edumazet-glaptop> <501D99C4.20902@pollere.com> <7EB59257-1A8E-4567-8AD3-5016594565CC@gmail.com> <1344144623.9299.1557.camel@edumazet-glaptop> <4A256974B5054317913BC067C4E5FAE1@srichardlxp2> <1344187557.9299.1610.camel@edumazet-glaptop> <1344188112.9299.1614.camel@edumazet-glaptop> <1344192037.9299.1618.camel@edumazet-glaptop> <8860AEB6C5DB43649852D9A8B40E9B9F@srichardlxp2> <1344271579.26674.45.camel@edumazet-glaptop> <441D6067-BC04-4461-BD91-4A988A089866@gmail.com> Content-Type: text/plain; charset="UTF-8" Date: Mon, 06 Aug 2012 22:01:09 +0200 Message-ID: <1344283269.26674.62.camel@edumazet-glaptop> Mime-Version: 1.0 X-Mailer: Evolution 2.28.3 Content-Transfer-Encoding: 7bit Cc: codel@lists.bufferbloat.net Subject: Re: [Codel] [RFC PATCH] codel: ecn mark at target X-BeenThere: codel@lists.bufferbloat.net X-Mailman-Version: 2.1.13 Precedence: list List-Id: CoDel AQM discussions List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Mon, 06 Aug 2012 20:01:15 -0000 On Mon, 2012-08-06 at 12:09 -0700, Andrew McGregor wrote: > On 6/08/2012, at 10:50 AM, Dave Taht wrote: > > > This discussion is getting mildly off-track. My intent in posting this patch > > was to prove how wrong the "ecn mark at target" idea was by example, > > and in doing so, shed light on those new to codel, on how the algorithm > > actually works, and to encourage those that didn't grok it, to read and > > run the code in whatever scenarios would help more people to > > grokking in fullness. > > > > I hadn't expected to twiddle a bug! > > Well, so drop at target is wrong wrt deployed TCPs. Ok, fine. > > So, instead, how about this: mark instead of dropping, but only for > the first few iterations around the while loop in dequeue (so that > huge backlogs can be drained). The question then is, how many is a > few? I suppose that can be answered empirically. > > Andrew Lets take the analogy with RED. Once a MAX_THRESH was reached, it did a hard_mark. So we could choose a threshold to drop instead of marking. Possible easy choices : 1) A threshold on sojourn time. For example force_drop = 2 * target 2) A threshold on 'count'. For example force_drop if count > 1000