From owner-freebsd-net@FreeBSD.ORG Wed Feb 6 17:28:44 2013 Return-Path: Delivered-To: net@freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:1900:2254:206a::19:1]) by hub.freebsd.org (Postfix) with ESMTP id CD141FFE; Wed, 6 Feb 2013 17:28:44 +0000 (UTC) (envelope-from bright@mu.org) Received: from elvis.mu.org (elvis.mu.org [192.203.228.196]) by mx1.freebsd.org (Postfix) with ESMTP id BB332CB4; Wed, 6 Feb 2013 17:28:44 +0000 (UTC) Received: from Alfreds-MacBook-Pro-9.local (c-67-180-208-218.hsd1.ca.comcast.net [67.180.208.218]) by elvis.mu.org (Postfix) with ESMTPSA id 1ABEE1A3C1B; Wed, 6 Feb 2013 09:28:42 -0800 (PST) Message-ID: <511292C9.4040307@mu.org> Date: Wed, 06 Feb 2013 09:28:41 -0800 From: Alfred Perlstein User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.7; rv:17.0) Gecko/20130107 Thunderbird/17.0.2 MIME-Version: 1.0 To: John Baldwin Subject: Re: [PATCH] Add a new TCP_IGNOREIDLE socket option References: <201301221511.02496.jhb@freebsd.org> <50FF06AD.402@networx.ch> <061B4EA5-6A93-48A0-A269-C2C3A3C7E77C@lakerest.net> <201302060746.43736.jhb@freebsd.org> In-Reply-To: <201302060746.43736.jhb@freebsd.org> Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Cc: Randall Stewart , net@freebsd.org X-BeenThere: freebsd-net@freebsd.org X-Mailman-Version: 2.1.14 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, 06 Feb 2013 17:28:44 -0000 On 2/6/13 4:46 AM, John Baldwin wrote: > On Wednesday, February 06, 2013 6:27:04 am Randall Stewart wrote: >> John: >> >> A burst at line rate will *often* cause drops. This is because >> router queues are at a finite size. Also such a burst (especially >> on a long delay bandwidth network) cause your RTT to increase even >> if there is no drop which is going to hurt you as well. >> >> A SHOULD in an RFC says you really really really really need to do it >> unless there is some thing that makes you willing to override it. It is >> slight wiggle room. >> >> In this I agree with Andre, we should not be *not* doing it. Otherwise >> folks will be turning this on and it is plain wrong. It may be fine >> for your network but I would not want to see it in FreeBSD. >> >> In my testing here at home I have put back into our stack max-burst. This >> uses Mark Allman's version (not Kacheong Poon's) where you clamp the cwnd at >> no more than 4 packets larger than your flight. All of my testing >> high-bw-delay or lan has shown this to improve TCP performance. This >> is because it helps you avoid bursting out so many packets that you overflow >> a queue. >> >> In your long-delay bw link if you do burst out too many (and you never >> know how many that is since you can not predict how full all those >> MPLS queues are or how big they are) you will really hurt yourself even worse. >> Note that generally in Cisco routers the default queue size is somewhere between >> 100-300 packets depending on the router. > Due to the way our application works this never happens, but I am fine with > just keeping this patch private. If there are other shops that need this they > can always dig the patch up from the archives. > This is yet another time when I'm sad about how things happen in FreeBSD. A developer come forward with a non-default option that's very useful for some specific workloads, specifically one that contributes much time and $$$ to the project and the community rejects the patches even though it's been successful in other OSes. It makes zero sense. John, can you repost the patch? Maybe there is a way to refactor this somehow so it's like accept filters where we can plug in a hook for TCP? I am very disappointed, but not surprised. -Alfred