From mboxrd@z Thu Jan 1 00:00:00 1970 From: "John Heffner" Subject: Re: setsockopt() Date: Mon, 7 Jul 2008 20:33:10 -0700 Message-ID: <1e41a3230807072033n2f5519e4m42003e191b44cefe@mail.gmail.com> References: <48725DFE.6000504@citi.umich.edu> <20080707142408.43aa2a2e@extreme> <48728B09.1050801@citi.umich.edu> <48729DAD.8010400@hp.com> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Cc: netdev@vger.kernel.org To: "Rick Jones" Return-path: Received: from an-out-0708.google.com ([209.85.132.241]:36596 "EHLO an-out-0708.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756125AbYGHDdN (ORCPT ); Mon, 7 Jul 2008 23:33:13 -0400 Received: by an-out-0708.google.com with SMTP id d40so474964and.103 for ; Mon, 07 Jul 2008 20:33:10 -0700 (PDT) In-Reply-To: <48729DAD.8010400@hp.com> Content-Disposition: inline Sender: netdev-owner@vger.kernel.org List-ID: On Mon, Jul 7, 2008 at 3:50 PM, Rick Jones wrote: > I'm still a triffle puzzled/concerned/confused by the extent to which > autotuning will allow the receive window to grow, again based on some > netperf experience thusfar, and patient explanations provided here and > elsewhere, it seems as though autotuning will let things get to 2x what it > thinks the sender's cwnd happens to be. So far under netperf testing that > seems to be the case, and 99 times out of ten my netperf tests will have the > window grow to the max. Rick, I thought this was covered pretty thoroughly back in April. The behavior you're seeing is 100% expected, and not likely to change unless Jerry Chu gets his local queued data measurement patch working. I'm not sure what ultimately happened there, but it was a cool idea and I hope he has time to polish it up. It's definitely tricky to get right. Jerry's optimization is a sender-side change. The fact that the receiver announces enough window is almost certainly the right thing for it to do, and (I hope) this will not change. If you're still curious: http://www.psc.edu/networking/ftp/papers/autotune_sigcomm98.ps http://www.lanl.gov/radiant/pubs/drs/lacsi2001.pdf http://staff.psc.edu/jheffner/papers/senior_thesis.pdf -John