From mboxrd@z Thu Jan 1 00:00:00 1970 From: Ben Greear Subject: Re: Question on TSO maximum segment sizes. Date: Thu, 11 Oct 2007 18:29:51 -0700 Message-ID: <470ECE0F.4060506@candelatech.com> References: <20071011.163737.36654032.davem@davemloft.net><470EB6D6.9020704@hp.com> <20071011.170244.32082446.davem@davemloft.net> <470EBD2C.8020704@candelatech.com> <470ECC71.1070303@psc.edu> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Cc: netdev@vger.kernel.org To: John Heffner Return-path: Received: from ns2.lanforge.com ([66.165.47.211]:47501 "EHLO ns2.lanforge.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753628AbXJLBaG (ORCPT ); Thu, 11 Oct 2007 21:30:06 -0400 In-Reply-To: <470ECC71.1070303@psc.edu> Sender: netdev-owner@vger.kernel.org List-Id: netdev.vger.kernel.org John Heffner wrote: > Ben Greear wrote: >> I just tried turning off my explicit SO_SNDBUF/SO_RCVBUG settings in >> my app, >> and the connection ran very poorly through a link with even a small >> bit of latency (~2-4ms I believe). > > I often run at full gigabit or faster with latencies of 100+ ms. Can > you give a bit more detail? I'm doing non-blocking TCP sends, write sizes of around 64k, and I'm doing this to/from the same system with the send-to-self patch. I am running full-duplex (930+Mbps tx + rx on both ports) (this is about 980Mbps on the wire). If I don't set the tx-queue % rx-queue sizes large (~4MB), it does not perform well when running through my latency emulator. If I do set them, then it runs just fine (barring an occassional TCP throughput deadlock & ACK storm that is being worked on separately.) If it works for other people, then it could be something else weird about my setup. I have an easy work-around (been in the code for years and years now), so I'm not too worried either way. Thanks, Ben > > -John -- Ben Greear Candela Technologies Inc http://www.candelatech.com