From owner-freebsd-arch@FreeBSD.ORG Sun Mar 21 16:53:49 2010 Return-Path: Delivered-To: freebsd-arch@freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:4f8:fff6::34]) by hub.freebsd.org (Postfix) with ESMTP id 6E89B1065670 for ; Sun, 21 Mar 2010 16:53:49 +0000 (UTC) (envelope-from uqs@spoerlein.net) Received: from acme.spoerlein.net (acme.spoerlein.net [188.72.220.29]) by mx1.freebsd.org (Postfix) with ESMTP id 14D738FC16 for ; Sun, 21 Mar 2010 16:53:48 +0000 (UTC) Received: from acme.spoerlein.net (localhost.spoerlein.net [IPv6:::1]) by acme.spoerlein.net (Postfix) with ESMTPS id F211D5C84; Sun, 21 Mar 2010 17:53:16 +0100 (CET) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=spoerlein.net; s=dkim200908; t=1269190397; bh=o2mmxpb8Ol6Va50nCfh3b6uJrRt/9DfdyoTAD/Y1P7E=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Transfer-Encoding:In-Reply-To; b=fdfvNQoZhGZYBjsrCRzcwHTFuWtrjlPR/nwEToJ6WwliOMvFz0s6o9ZQ9wZhWIaue STSEHXx4+CCJFhWAKhDVbhB6oZtB0tmrUAgmS9AuszZsqauCyvRsFqWM6GGeFJLbI1 Zmo3+kP9OT6gXzJGI4kPw2YvYdPwmb0dYcw/ZeX4= Received: (from uqs@localhost) by acme.spoerlein.net (8.14.4/8.14.4/Submit) id o2LGrGoJ089397; Sun, 21 Mar 2010 17:53:16 +0100 (CET) (envelope-from uqs@spoerlein.net) Date: Sun, 21 Mar 2010 17:53:16 +0100 From: Ulrich =?utf-8?B?U3DDtnJsZWlu?= To: Scott Long Message-ID: <20100321165316.GU99813@acme.spoerlein.net> Mail-Followup-To: Scott Long , freebsd-current@freebsd.org, freebsd-arch@freebsd.org References: <4BA4E7A9.3070502@FreeBSD.org> <201003201753.o2KHrH5x003946@apollo.backplane.com> <891E2580-8DE3-4B82-81C4-F2C07735A854@samsco.org> <20100321163051.GT99813@acme.spoerlein.net> <9524C333-F191-4F7A-A5FA-BD52498169C0@samsco.org> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <9524C333-F191-4F7A-A5FA-BD52498169C0@samsco.org> User-Agent: Mutt/1.5.20 (2009-06-14) Cc: freebsd-current@freebsd.org, freebsd-arch@freebsd.org Subject: Re: Increasing MAXPHYS X-BeenThere: freebsd-arch@freebsd.org X-Mailman-Version: 2.1.5 Precedence: list List-Id: Discussion related to FreeBSD architecture List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Sun, 21 Mar 2010 16:53:49 -0000 [CC trimmed] On Sun, 21.03.2010 at 10:39:10 -0600, Scott Long wrote: > On Mar 21, 2010, at 10:30 AM, Ulrich Spörlein 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. > > > > Hi Scott, > > > > 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? > > > > 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? All true, that's why I wanted to know from you, which real world situations you encountered where FreeBSD did/does outperform Linux in regards to I/O throughput and/or latency (depending on scenario, of course). I hope you don't mind, Uli