From owner-freebsd-net@FreeBSD.ORG Thu Aug 4 14:31:20 2011 Return-Path: Delivered-To: freebsd-net@freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:4f8:fff6::34]) by hub.freebsd.org (Postfix) with ESMTP id 70817106564A; Thu, 4 Aug 2011 14:31:20 +0000 (UTC) (envelope-from prvs=11971cf4bd=killing@multiplay.co.uk) Received: from mail1.multiplay.co.uk (mail1.multiplay.co.uk [85.236.96.23]) by mx1.freebsd.org (Postfix) with ESMTP id 87CEC8FC1E; Thu, 4 Aug 2011 14:31:19 +0000 (UTC) X-MDAV-Processed: mail1.multiplay.co.uk, Thu, 04 Aug 2011 15:19:19 +0100 X-Spam-Processed: mail1.multiplay.co.uk, Thu, 04 Aug 2011 15:19:19 +0100 X-Spam-Checker-Version: SpamAssassin 3.2.5 (2008-06-10) on mail1.multiplay.co.uk X-Spam-Level: X-Spam-Status: No, score=-5.0 required=6.0 tests=USER_IN_WHITELIST shortcircuit=ham autolearn=disabled version=3.2.5 Received: from r2d2 ([188.220.16.49]) by mail1.multiplay.co.uk (mail1.multiplay.co.uk [85.236.96.23]) (MDaemon PRO v10.0.4) with ESMTP id md50014465425.msg; Thu, 04 Aug 2011 15:19:19 +0100 X-MDRemoteIP: 188.220.16.49 X-Return-Path: prvs=11971cf4bd=killing@multiplay.co.uk X-Envelope-From: killing@multiplay.co.uk Message-ID: <20229216858044E4881642284F245750@multiplay.co.uk> From: "Steven Hartland" To: "Lawrence Stewart" References: <1F95A4C2D54E4F369830143CBDB5FF86@multiplay.co.uk><4E37C0F2.4080004@freebsd.org> <2B063B6D95AA4C27B004C50D96393F91@multiplay.co.uk> <4E3AA66A.6060605@freebsd.org> Date: Thu, 4 Aug 2011 15:19:54 +0100 MIME-Version: 1.0 Content-Type: text/plain; format=flowed; charset="iso-8859-1"; reply-type=response Content-Transfer-Encoding: 7bit X-Priority: 3 X-MSMail-Priority: Normal X-Mailer: Microsoft Outlook Express 6.00.2900.5931 X-MimeOLE: Produced By Microsoft MimeOLE V6.00.2900.6109 Cc: freebsd-net@freebsd.org, Andre Oppermann , slw@zxy.spb.ru Subject: Re: tcp failing to recover from a packet loss under 8.2-RELEASE? X-BeenThere: freebsd-net@freebsd.org X-Mailman-Version: 2.1.5 Precedence: list List-Id: Networking and TCP/IP with FreeBSD List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Thu, 04 Aug 2011 14:31:20 -0000 ----- Original Message ----- From: "Lawrence Stewart" > Thanks for bringing me in directly, I haven't been keeping up with the > mailing lists at all recently. No problem >> So I suppose the question is should maxsegments be larger by >> default due to the recent changes e.g. >> - V_tcp_reass_maxseg = nmbclusters / 16; >> + V_tcp_reass_maxseg = nmbclusters / 8; >> >> or is the correct fix something more involved? > > I'm not sure if bumping the value is appropriate - we have always > expected users to tune their network stack to perform well when used in > "unusual" scenarios - a large BDP fibre path still being in the > "unusual" category. TBH I wouldn't classify a latency of 7ms @ 100Mbps unusal in the slightest in this day and age. > The real fix which is somewhere down on my todo list is to make all > these memory constraints elastic and respond to VM pressure, thus > negating the need for a hard limit at all. This would solve many if not > most of the TCP tuning problems we currently have with one foul swoop > and would greatly reduce the need for tuning in many situations that > currently are in the "needs manual tuning" basket. This would indeed be a great improvement. > Andre and Steven, I'm a bit too sleepy to properly review your combined > proposed changes right now and will follow up in the next few days instead. No problem, we've increased nmbclusters on all our machines and there now performing fine in the problem scenario so no rush, look forward to your feedback when you've had some sleep :) Regards Steve ================================================ This e.mail is private and confidential between Multiplay (UK) Ltd. and the person or entity to whom it is addressed. In the event of misdirection, the recipient is prohibited from using, copying, printing or otherwise disseminating it or any information contained in it. In the event of misdirection, illegible or incomplete transmission please telephone +44 845 868 1337 or return the E.mail to postmaster@multiplay.co.uk.