From mboxrd@z Thu Jan 1 00:00:00 1970 From: "SANGTAE HA" Subject: Re: SACK scoreboard Date: Wed, 9 Jan 2008 13:14:22 -0500 Message-ID: <649aecc70801091014u50d1be26ndf5e59e0492ce9cd@mail.gmail.com> References: <20080108.144456.173014334.davem@davemloft.net> <47844D1C.1060706@psc.edu> <20080108.224144.234253941.davem@davemloft.net> <4784E090.8080303@psc.edu> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Cc: "David Miller" , andi@firstfloor.org, ilpo.jarvinen@helsinki.fi, lachlan.andrew@gmail.com, netdev@vger.kernel.org, quetchen@caltech.edu To: "John Heffner" Return-path: Received: from wx-out-0506.google.com ([66.249.82.229]:60072 "EHLO wx-out-0506.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754140AbYAISOZ (ORCPT ); Wed, 9 Jan 2008 13:14:25 -0500 Received: by wx-out-0506.google.com with SMTP id h31so182934wxd.4 for ; Wed, 09 Jan 2008 10:14:24 -0800 (PST) In-Reply-To: <4784E090.8080303@psc.edu> Content-Disposition: inline Sender: netdev-owner@vger.kernel.org List-ID: On Jan 9, 2008 9:56 AM, John Heffner wrote: > >> I also wonder how much of a problem this is (for now, with window sizes > >> of order 10000 packets. My understanding is that the biggest problems > >> arise from O(N^2) time for recovery because every ack was expensive. > >> Have current tests shown the final ack to be a major source of problems? > > > > Yes, several people have reported this. > > I may have missed some of this. Does anyone have a link to some recent > data? I had some testing on this a month ago. A small set of recent results with linux 2.6.23.9 are at http://netsrv.csc.ncsu.edu/net-2.6.23.9/sack_efficiency One of serious cases with a large number of packet losses (initial loss is around 8000 packets) is at http://netsrv.csc.ncsu.edu/net-2.6.23.9/sack_efficiency/600--TCP-TCP-NONE--400-3-1.0--1000-120-0-0-1-1-5-500--1.0-0.5-133000-73-3000000-0.93-150--3/ Also, there is a comparison among three Linux kernels (2.6.13, 2.6.18-rc4, 2.6.20.3) at http://netsrv.csc.ncsu.edu/wiki/index.php/Efficiency_of_SACK_processing Sangtae