From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-03-iad.dyndns.com (mxout-110-iad.mailhop.org [216.146.32.110]) by lists.bufferbloat.net (Postfix) with ESMTP id 09BFA2E0271 for ; Tue, 15 Mar 2011 18:28:58 -0700 (PDT) Received: from scan-02-iad.mailhop.org (scan-02-iad.local [10.150.0.207]) by mail-03-iad.dyndns.com (Postfix) with ESMTP id 8CA7F834B00 for ; Wed, 16 Mar 2011 01:29:00 +0000 (UTC) X-Spam-Score: -1.0 (-) X-Mail-Handler: MailHop by DynDNS X-Originating-IP: 74.125.82.171 Received: from mail-wy0-f171.google.com (mail-wy0-f171.google.com [74.125.82.171]) by mail-03-iad.dyndns.com (Postfix) with ESMTP id 7848E834ABD for ; Wed, 16 Mar 2011 01:28:59 +0000 (UTC) Received: by wyb32 with SMTP id 32so1434764wyb.16 for ; Tue, 15 Mar 2011 18:28:56 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=gamma; h=domainkey-signature:subject:mime-version:content-type:from :in-reply-to:date:cc:content-transfer-encoding:message-id:references :to:x-mailer; bh=WAJmvk0K67trUVOMGoevWaHNIFeilRKDmNP4ZwtJlEI=; b=CjKDUT8apUaEfTZFCXPiZBXAk9v3+z0XTnBvl3voczjpdwuI8WN8mHUyyQDlNDI7QB Q6tVFKRof0RCCnU9nOdvxe6Tq7TSolyLJ2CdOL36E2yYyDQi6QrCCmpEXONZXieVi+ph 2ijWTUec842aJQ37cjf5IAwRY/YhF+9xXjMbg= DomainKey-Signature: a=rsa-sha1; c=nofws; d=gmail.com; s=gamma; h=subject:mime-version:content-type:from:in-reply-to:date:cc :content-transfer-encoding:message-id:references:to:x-mailer; b=Lsvd9G9pCIBKQasKeSKuSWenaH87hCjC6ajytY6vs+Q5MVFqHoCcpw/KcaQQFic1Qp ZPqMzJL5Bjq0hHZir5agjkd8Vt9HjN2Y0DrlbhROaVNzT506Ou8+S450WeylQQivOaTU OpICHo4/MkKGnPxmMDed61iZG0VXuMH9+yG5c= Received: by 10.227.179.68 with SMTP id bp4mr175743wbb.93.1300238936613; Tue, 15 Mar 2011 18:28:56 -0700 (PDT) Received: from [192.168.239.42] (xdsl-83-150-84-172.nebulazone.fi [83.150.84.172]) by mx.google.com with ESMTPS id bd8sm464812wbb.7.2011.03.15.18.28.55 (version=TLSv1/SSLv3 cipher=OTHER); Tue, 15 Mar 2011 18:28:56 -0700 (PDT) Mime-Version: 1.0 (Apple Message framework v1082) Content-Type: text/plain; charset=iso-8859-1 From: Jonathan Morton In-Reply-To: <87bp1b6fo0.fsf@cruithne.co.teklibre.org> Date: Wed, 16 Mar 2011 03:28:54 +0200 Content-Transfer-Encoding: quoted-printable Message-Id: References: <4D7F4121.40307@freedesktop.org> <20110315175942.GA10064@goldfish> <1300212877.2087.2155.camel@tardy> <20110315183111.GB2542@tuxdriver.com> <29B06777-CC5F-4802-8727-B04F58CDA9E3@gmail.com> <20110315205146.GF2542@tuxdriver.com> <219C7840-ED79-49EA-929D-96C5A6200401@gmail.com> <20110315151946.31e86b46@nehalam> <1300228592.2087.2191.camel@tardy> <1300229578.2565.29.camel@edumazet-laptop> <87fwqo54n7.fsf@cruithne.co.teklibre.org> <823E2A7B-4F46-4159-8029-BD3B075CC4CE@gmail.com> <87bp1b6fo0.fsf@cruithne.co.teklibre.org> To: d@taht.net (=?iso-8859-1?Q?Dave_T=E4ht?=) X-Mailer: Apple Mail (2.1082) Cc: Stephen Hemminger , bloat@lists.bufferbloat.net Subject: Re: [Bloat] Random idea in reaction to all the discussion of TCP flavours - timestamps? X-BeenThere: bloat@lists.bufferbloat.net X-Mailman-Version: 2.1.13 Precedence: list List-Id: General list for discussing Bufferbloat List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Wed, 16 Mar 2011 01:28:59 -0000 On 16 Mar, 2011, at 3:02 am, Dave T=E4ht wrote: >>>> 1) Wired devices, where we want to push more 10+ Gbps, so we can = assume >>>> a posted skb is transmitted immediately. Even a basic qdisc can be = a >>>> performance bottleneck. Set TX ring size to 256 or 1024+ buffers to >>>> avoid taking too many interrupts. >>>=20 >>> To talk to this a bit, the huge dynamic range discrepancy between a >>> 10GigE device and what it may be connected to worries me. Some form = of >>> fair queuing should be applied before the data hits the driver. >>=20 >> You mean plugging a 10GigE card into a 10Base-T hub? :-D >=20 > More like 10GigE into a 1Gig switch. Or spewing out the entire = contents > of a stream to one destination across the internet.=20 Then that's no different to what I have in my apartment right now - a = GigE switch connected to a 100base-TX switch, then to a 2Mbps DSL = uplink, which could then be routed (after bouncing around backhauls for = a bit) through a 500Kbps 3G downlink to a computer I've isolated from = the LAN. If the flow is responsive, as with every sane TCP, the queue will end up = in front of the slowest link - at the 3G tower. That's where the AQM = would need to be. The GigE adapter in my nettop would be largely idle, = as a normal function of the TCP congestion window. If it isn't, the queue will build up at *every* narrowing of the channel = and the packet loss will be astronomical. All AQM could do then is to = pick any real traffic out of the din. - Jonathan