From owner-freebsd-current@FreeBSD.ORG Sun Mar 21 16:39:20 2010 Return-Path: Delivered-To: freebsd-current@freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:4f8:fff6::34]) by hub.freebsd.org (Postfix) with ESMTP id 46AB3106566C; Sun, 21 Mar 2010 16:39:20 +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 DA6AB8FC0C; Sun, 21 Mar 2010 16:39:19 +0000 (UTC) Received: from phobos.samsco.home (phobos.samsco.home [192.168.254.11]) (authenticated bits=0) by pooker.samsco.org (8.14.3/8.14.3) with ESMTP id o2LGdAUv036941; Sun, 21 Mar 2010 10:39:10 -0600 (MDT) (envelope-from scottl@samsco.org) Mime-Version: 1.0 (Apple Message framework v1077) Content-Type: text/plain; charset=iso-8859-1 From: Scott Long In-Reply-To: <20100321163051.GT99813@acme.spoerlein.net> Date: Sun, 21 Mar 2010 10:39:10 -0600 Content-Transfer-Encoding: quoted-printable Message-Id: <9524C333-F191-4F7A-A5FA-BD52498169C0@samsco.org> References: <4BA4E7A9.3070502@FreeBSD.org> <201003201753.o2KHrH5x003946@apollo.backplane.com> <891E2580-8DE3-4B82-81C4-F2C07735A854@samsco.org> <20100321163051.GT99813@acme.spoerlein.net> To: =?iso-8859-1?Q?Ulrich_Sp=F6rlein?= X-Mailer: Apple Mail (2.1077) X-Spam-Status: No, score=-1.0 required=3.8 tests=ALL_TRUSTED autolearn=unavailable version=3.3.0 X-Spam-Checker-Version: SpamAssassin 3.3.0 (2010-01-18) on pooker.samsco.org Cc: freebsd-current@freebsd.org, Alexander Motin , freebsd-arch@freebsd.org Subject: Re: Increasing MAXPHYS X-BeenThere: freebsd-current@freebsd.org X-Mailman-Version: 2.1.5 Precedence: list List-Id: Discussions about the use of FreeBSD-current List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Sun, 21 Mar 2010 16:39:20 -0000 On Mar 21, 2010, at 10:30 AM, Ulrich Sp=F6rlein wrote: > On Sat, 20.03.2010 at 12:17:33 -0600, Scott Long wrote: >> Windows has a MAXPHYS equivalent of 1M. Linux has an equivalent of = an >> odd number less than 512k. For the purpose of benchmarking against = these >> OS's, having comparable capabilities is essential; Linux easily beats = FreeBSD >> in the silly-i/o-test because of the MAXPHYS difference (though = FreeBSD typically >> stomps linux in real I/O because of vastly better latency and caching = algorithms). >> I'm fine with raising MAXPHYS in production once the problems are = addressed. >=20 > Hi Scott, >=20 > while I'm sure that most of the FreeBSD admins are aware of "silly" > benchmarks where Linux I/O seems to dwarf FreeBSD, do you have some > pointers regarding your statement that FreeBSD triumphs for real-world > I/O loads? Can this be simulated using iozone, bonnie, etc? More > importantly, is there a way to do this file system independently? >=20 iozone and bonnie tend to be good at testing serialized I/O latency; = each read and write is serialized without any buffering. My experience = is that they give mixed results, sometimes they favor freebsd, sometime = linux, sometimes it's a wash, all because they are so sensitive to = latency. And that's where is also gets hard to have a "universal" = benchmark; what are you really trying to model, and how does that model = reflect your actual workload? Are you running a single-instance, single = threaded application that is sensitive to latency? Are you running a = multi-instance/multi-threaded app that is sensitive to bandwidth? Are = you operating on a single file, or on a large tree of files, or on a raw = device? Are you sharing a small number of relatively stable file = descriptors, or constantly creating and deleting files and truncating = space?=