From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-01-iad.dyndns.com (mxout-234-iad.mailhop.org [216.146.32.234]) by lists.bufferbloat.net (Postfix) with ESMTP id B55DB2E0117 for ; Fri, 25 Feb 2011 08:34:14 -0800 (PST) Received: from scan-01-iad.mailhop.org (scan-01-iad.local [10.150.0.206]) by mail-01-iad.dyndns.com (Postfix) with ESMTP id 4B4966E278 for ; Fri, 25 Feb 2011 16:33:58 +0000 (UTC) X-Spam-Score: -1.0 (-) X-Mail-Handler: MailHop by DynDNS X-Originating-IP: 209.85.214.43 Received: from mail-bw0-f43.google.com (mail-bw0-f43.google.com [209.85.214.43]) by mail-01-iad.dyndns.com (Postfix) with ESMTP id 646726DEBC; Fri, 25 Feb 2011 16:33:57 +0000 (UTC) Received: by bwz14 with SMTP id 14so2639563bwz.16 for ; Fri, 25 Feb 2011 08:33:56 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=gamma; h=domainkey-signature:subject:from:to:cc:in-reply-to:references :content-type:date:message-id:mime-version:x-mailer :content-transfer-encoding; bh=2+ZWYl/umx5J4p2YCzGY6O9G+t9OomLob6sX5yPeWrQ=; b=JEaJIGu7GH2/oRNwZlciojnaN9T1/TumxR5K1K1BKDiFvyWSZ9vO/QeYggFSRaxYVh Buv+Uh4T96/chow6QRx8R0U59ozUdy/R+Qwe3xrX/XgCDMkDbMRfvyVZdTsFJxYWV8oi QKP9QFdTqAnzwUHcCjlwWkHQp6jiL9GppNnKA= DomainKey-Signature: a=rsa-sha1; c=nofws; d=gmail.com; s=gamma; h=subject:from:to:cc:in-reply-to:references:content-type:date :message-id:mime-version:x-mailer:content-transfer-encoding; b=b0uWlyr+O5KYeTN8ILmMxfUNuG0eJVc4gcsOemmGxjnavOhyjCnzf+wxapjH5cw/Bx K2Tn7OwhcY+tevC5L8mbfeaBe5E+0yAB894l09DlVztOZviNLy1KimnGWaTg2Q7qwzuQ +c6uaYn88anEpgy3qNZCmFh2JW4v82lMjaxYY= Received: by 10.204.7.86 with SMTP id c22mr869909bkc.66.1298651633508; Fri, 25 Feb 2011 08:33:53 -0800 (PST) Received: from [10.150.51.210] (gw0.net.jmsp.net [212.23.165.14]) by mx.google.com with ESMTPS id v25sm536307bkt.18.2011.02.25.08.33.51 (version=SSLv3 cipher=OTHER); Fri, 25 Feb 2011 08:33:52 -0800 (PST) Subject: Re: GSO (was: Please enter issues into the issue tracker - Issue system organisation needed) From: Eric Dumazet To: Jesper Dangaard Brouer In-Reply-To: <1298648937.28000.41.camel@traveldev.cxnet.dk> References: <4D6668F4.5010705@freedesktop.org> <4D668827.8060508@freedesktop.org> <1298567313.2814.7.camel@edumazet-laptop> <87sjvds2r7.fsf@cruithne.co.teklibre.org> <1298575769.2659.10.camel@edumazet-laptop> <1298632912.21810.33.camel@traveldev.cxnet.dk> <1298634859.2659.44.camel@edumazet-laptop> <1298648937.28000.41.camel@traveldev.cxnet.dk> Content-Type: text/plain; charset="UTF-8" Date: Fri, 25 Feb 2011 17:33:47 +0100 Message-ID: <1298651627.2659.84.camel@edumazet-laptop> Mime-Version: 1.0 X-Mailer: Evolution 2.30.3 Content-Transfer-Encoding: 8bit Cc: Van Jacobson , bloat-devel@lists.bufferbloat.net, herbert@gondor.apana.org.au, bloat@lists.bufferbloat.net X-BeenThere: bloat-devel@lists.bufferbloat.net X-Mailman-Version: 2.1.13 Precedence: list List-Id: "Developers working on AQM, device drivers, and networking stacks" List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Fri, 25 Feb 2011 16:34:15 -0000 Le vendredi 25 février 2011 à 16:48 +0100, Jesper Dangaard Brouer a écrit : > Yes, both servers (/proc/sys/net/ipv4/tcp_sack = 1). > > I think that the bufferbloat theory is that SACKs will not work, due to > the long delays introduced by buffers(bloat). In this case, you can > see on the graph, a max RTT around 150 ms and an average of 20 ms. > > While another, more well behaved path in the network to the speed > server, I would only see a max RTT around 25 ms and an average of 15 ms, > see: > http://people.netfilter.org/hawk/dropbox/bloat_vs_GSO/speed-to-pc314a-1.png > > You can also see this path had an ave of 90Mbit/s, but with significant > throughput drops (the 92Mbit/s line is an artificial line on the graph). > This behavior is probaly caused by the GSO effect. > > Disabling GSO on speed server fixed the problem as can be seen on graph: > http://people.netfilter.org/hawk/dropbox/bloat_vs_GSO/speed-to-grantoften-solved.png > > The really strange part when troubleshooting this issue was that the > throughput as fine between the two customer end-boxes ("grantoften" and > "pc314a") as can be see here: > http://people.netfilter.org/hawk/dropbox/bloat_vs_GSO/pc314a-to-grantoften-1.png > > Its a bit hard to interpret these graphs, I am a bit lost... What exactly is sampled ? Is it from tcpdump analysis or output from HTB/SFQ stats ? For sure, one TSO drop really drops a full range of [XX] tcp segments, while with TSO off, a drop is one segment drop. This certainly can explain bad artifacts, as receiver interprets this as a huge congestion indication. TSO/GRO are good only in the datacenter domain, where we want 10Gb flows between two nodes with low CPU impact.