From owner-freebsd-net@FreeBSD.ORG Fri Jan 24 23:05:59 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 58B72DD5 for ; Fri, 24 Jan 2014 23:05:59 +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 2FE321228 for ; Fri, 24 Jan 2014 23:05:58 +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 s0ON5vtJ005714 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-SHA bits=256 verify=NO); Fri, 24 Jan 2014 15:05:58 -0800 (PST) (envelope-from jmg@h2.funkthat.com) Received: (from jmg@localhost) by h2.funkthat.com (8.14.3/8.14.3/Submit) id s0ON5vBH005713; Fri, 24 Jan 2014 15:05:57 -0800 (PST) (envelope-from jmg) Date: Fri, 24 Jan 2014 15:05:57 -0800 From: John-Mark Gurney To: Rick Macklem Subject: Re: Terrible NFS performance under 9.2-RELEASE? Message-ID: <20140124230557.GF75135@funkthat.com> Mail-Followup-To: Rick Macklem , J David , freebsd-net@freebsd.org References: <659117348.16015750.1390604069888.JavaMail.root@uoguelph.ca> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <659117348.16015750.1390604069888.JavaMail.root@uoguelph.ca> 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-to-the-FBI-CIA-and-NSA: HI! HOW YA DOIN? can i haz chizburger? X-Greylist: Sender passed SPF test, not delayed by milter-greylist-4.2.2 (h2.funkthat.com [127.0.0.1]); Fri, 24 Jan 2014 15:05:58 -0800 (PST) Cc: freebsd-net@freebsd.org, J David 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: Fri, 24 Jan 2014 23:05:59 -0000 Rick Macklem wrote this message on Fri, Jan 24, 2014 at 17:54 -0500: > The largest jumbo packet supported by the generic mbuf code is 16K > (or maybe 9K for 9.2). I have no idea if this matters or not. This is only partly true. Our allocators only supports mbufs of 2k (standard size), 4k (page size), 9216 and 16184... If you allocate a 9k or 16k mbuf, it is guaranteed that the data will be physically contiguous so that cards that can't do scatter/gather DMA can handle larger frames... But if the card can handle S/G DMA, they can send a 32KB packet made up of normal 2k clusters, or any other odd sized mbufs... There are only a couple drivers (and I plan on working to remove the limit) that limit the size of MTU, but if the driver hardware supports it, there is nothing in our stack preventing large, as in 64KB, MTU use.. -- John-Mark Gurney Voice: +1 415 225 5579 "All that I will do, has been done, All that I have, has not."