From owner-freebsd-stable@FreeBSD.ORG Sat Feb 14 14:33:29 2009 Return-Path: Delivered-To: freebsd-stable@freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:4f8:fff6::34]) by hub.freebsd.org (Postfix) with ESMTP id 9A8561065672; Sat, 14 Feb 2009 14:33:29 +0000 (UTC) (envelope-from scottl@samsco.org) Received: from pooker.samsco.org (pooker.samsco.org [168.103.85.57]) by mx1.freebsd.org (Postfix) with ESMTP id 4B09C8FC14; Sat, 14 Feb 2009 14:33:29 +0000 (UTC) (envelope-from scottl@samsco.org) Received: from phobos.local ([192.168.254.200]) (authenticated bits=0) by pooker.samsco.org (8.14.2/8.14.2) with ESMTP id n1EEXPnJ078537; Sat, 14 Feb 2009 07:33:25 -0700 (MST) (envelope-from scottl@samsco.org) Message-ID: <4996D635.3000802@samsco.org> Date: Sat, 14 Feb 2009 07:33:25 -0700 From: Scott Long User-Agent: Mozilla/5.0 (Macintosh; U; Intel Mac OS X; en-US; rv:1.8.1.13) Gecko/20080313 SeaMonkey/1.1.9 MIME-Version: 1.0 To: Ivan Voras References: <499551B9.7050805@samsco.org> <4995DFE5.1020205@samsco.org> <9bbcef730902131421r53efa13dq371658888747f387@mail.gmail.com> In-Reply-To: <9bbcef730902131421r53efa13dq371658888747f387@mail.gmail.com> X-Enigmail-Version: 0.95.6 Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-Spam-Status: No, score=-4.4 required=3.8 tests=ALL_TRUSTED,BAYES_00 autolearn=ham version=3.1.8 X-Spam-Checker-Version: SpamAssassin 3.1.8 (2007-02-13) on pooker.samsco.org Cc: freebsd-current@freebsd.org, freebsd-stable@freebsd.org Subject: Re: HEADS UP: Major CAM performance regression X-BeenThere: freebsd-stable@freebsd.org X-Mailman-Version: 2.1.5 Precedence: list List-Id: Production branch of FreeBSD source code List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Sat, 14 Feb 2009 14:33:30 -0000 Ivan Voras wrote: > 2009/2/13 Scott Long : >> Ivan Voras wrote: >>> Scott Long wrote: >>> >>>> I have committed a fix for this problem for FreeBSD 8-CURRENT as of SVN >>>> revision 188570. FreeBSD 7-STABLE will be updated with the fix in a few >>>> days once I've gotten confirmation that the fix works and doesn't cause >>>> any adverse side-effects. Anyone wanting to help in this validation >>>> effort should apply the attached patch to their kernel source tree and >>>> recompile. Please contact me directly by email to report if the problem >>>> is fixed for you. >>> I notice that write performance on an ESXi 3.5 hosted system is doubled, >>> but read performance remains the same (in bonnie++). >>> On a CISS system there is no significant change. >> bonnie is an unreliable tool for measuring performance. > > I'll try your suggestion if you have one. I don't have a magic universal testing suite in my back pocket, sorry. You need to look at your expected workload and develop tests to simulate it. When I do testing during driver development, I try a lot of different parallel, sequential, large i/o, and small i/o combinations. > > (except if it's about bonnie++ primarily measuring sequential > read/write - if a system can't do sequential IO well, it probably > won't do random IO well) This is completely false. Disks can't do sequential i/o very well due to the physical limits of long seek times, but those seek times can be greatly amortized, even in a random workload, with tagged queueing and parallel dispatch from the OS. Bonnie simply cannot exercise this very well. Bonnie tests system latency for discrete I/O's. That is all it tests. Scott