From owner-freebsd-net@FreeBSD.ORG Wed Feb 26 21:24:13 2014 Return-Path: Delivered-To: freebsd-net@freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [8.8.178.115]) (using TLSv1 with cipher ADH-AES256-SHA (256/256 bits)) (No client certificate requested) by hub.freebsd.org (Postfix) with ESMTPS id B1A20148 for ; Wed, 26 Feb 2014 21:24:13 +0000 (UTC) Received: from h2.funkthat.com (gate2.funkthat.com [208.87.223.18]) (using TLSv1 with cipher DHE-RSA-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.freebsd.org (Postfix) with ESMTPS id 897F91D73 for ; Wed, 26 Feb 2014 21:24:13 +0000 (UTC) Received: from h2.funkthat.com (localhost [127.0.0.1]) by h2.funkthat.com (8.14.3/8.14.3) with ESMTP id s1QLOCL8041069 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-SHA bits=256 verify=NO); Wed, 26 Feb 2014 13:24:13 -0800 (PST) (envelope-from jmg@h2.funkthat.com) Received: (from jmg@localhost) by h2.funkthat.com (8.14.3/8.14.3/Submit) id s1QLOCNY041068; Wed, 26 Feb 2014 13:24:12 -0800 (PST) (envelope-from jmg) Date: Wed, 26 Feb 2014 13:24:12 -0800 From: John-Mark Gurney To: Jack Vogel Subject: Re: TSO Message-ID: <20140226212412.GZ92037@funkthat.com> Mail-Followup-To: Jack Vogel , Sami Halabi , FreeBSD Net References: <20140226180736.GV92037@funkthat.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.4.2.3i X-Operating-System: FreeBSD 7.2-RELEASE i386 X-PGP-Fingerprint: 54BA 873B 6515 3F10 9E88 9322 9CB1 8F74 6D3F A396 X-Files: The truth is out there X-URL: http://resnet.uoregon.edu/~gurney_j/ X-Resume: http://resnet.uoregon.edu/~gurney_j/resume.html X-TipJar: bitcoin:13Qmb6AeTgQecazTWph4XasEsP7nGRbAPE X-to-the-FBI-CIA-and-NSA: HI! HOW YA DOIN? can i haz chizburger? X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.2.2 (h2.funkthat.com [127.0.0.1]); Wed, 26 Feb 2014 13:24:13 -0800 (PST) Cc: FreeBSD Net , Sami Halabi X-BeenThere: freebsd-net@freebsd.org X-Mailman-Version: 2.1.17 Precedence: list List-Id: Networking and TCP/IP with FreeBSD List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Wed, 26 Feb 2014 21:24:13 -0000 Jack Vogel wrote this message on Wed, Feb 26, 2014 at 10:27 -0800: > Drivers have to work with whatever the requirements/limitations of the > hardware, > if you have a 5 lb sack you shouldn't be surprised if some drops when you > shove > 6 lbs at it :) But right now, when that happens, the nic just drops it instead of telling the kernel to stop giving 6 lbs sacks.. :) It's only after a large amount of work by various people did we even find out that this is what was happening... > Why not have this limit in the interface so the stack can avoid exceeding > it? One of the patches proposed does that, though I hope that ALL drivers will be properly updated when the patch hits the tree... > On Wed, Feb 26, 2014 at 10:07 AM, John-Mark Gurney wrote: > > > Sami Halabi wrote this message on Wed, Feb 26, 2014 at 19:37 +0200: > > > I'm reading (almost) all mailing emails in mailig list... > > > > > > Almost every / many problem in network performancr / packets loss ended > > up > > > suggesting disabling TSO. > > > > > > I wonder why.. Is it a bug in the implementation? Or bybdesign? > > > What are the usecases that TSO is needed? Myabe it should be disabled bt > > > default? > > > > It looks like most of the problems are in drivers that don't handle > > packets with a large number of segments properly... The problem is > > that some drivers limit to how segments a packet can be broken into, and > > then if they receive such a packet, instead of doing their darnest to > > deliver it, they drop it... > > > > There are some patches that help address the issue... > > > > Drivers should complain more loudly when a packet gets dropped by the > > driver, since it is likely that the OS may retry the same packet, > > just to have it fail, though sometimes it'll try a different set, and > > it might go through, so all the user may notice is a slight lag if > > they notice anything at all... -- John-Mark Gurney Voice: +1 415 225 5579 "All that I will do, has been done, All that I have, has not."