Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752884AbXHJEC5 (ORCPT ); Fri, 10 Aug 2007 00:02:57 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1750714AbXHJECs (ORCPT ); Fri, 10 Aug 2007 00:02:48 -0400 Received: from mail.tmr.com ([64.65.253.246]:60767 "EHLO gaimboi.tmr.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750710AbXHJECq convert rfc822-to-8bit (ORCPT ); Fri, 10 Aug 2007 00:02:46 -0400 Message-ID: <46BBE3DD.2090209@tmr.com> Date: Fri, 10 Aug 2007 00:04:45 -0400 From: Bill Davidsen User-Agent: Mozilla/5.0 (X11; U; Linux i686; en-US; rv:1.8.0.8) Gecko/20061105 SeaMonkey/1.0.6 MIME-Version: 1.0 To: david@lang.hm CC: Diego Calleja , Ingo Molnar , Alan Cox , J??rn Engel , Jeff Garzik , Linus Torvalds , Peter Zijlstra , linux-mm@kvack.org, Linux Kernel Mailing List , miklos@szeredi.hu, akpm@linux-foundation.org, neilb@suse.de, dgc@sgi.com, tomoki.sekiyama.qu@hitachi.com, nikita@clusterfs.com, trond.myklebust@fys.uio.no, yingchao.zhou@gmail.com, richard@rsk.demon.co.uk Subject: Re: [PATCH 00/23] per device dirty throttling -v8 References: <20070804103347.GA1956@elte.hu> <20070804163733.GA31001@elte.hu> <46B4C0A8.1000902@garzik.org> <20070804191205.GA24723@lazybastard.org> <20070804192130.GA25346@elte.hu> <20070804211156.5f600d80@the-village.bc.nu> <20070804202830.GA4538@elte.hu> <20070804224834.5187f9b7@the-village.bc.nu> <20070805071320.GC515@elte.hu> <20070805152231.aba9428a.diegocg@gmail.com> In-Reply-To: Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 8BIT Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2345 Lines: 57 david@lang.hm wrote: > On Sun, 5 Aug 2007, Diego Calleja wrote: > >> El Sun, 5 Aug 2007 09:13:20 +0200, Ingo Molnar escribi?: >> >>> Measurements show that noatime helps 20-30% on regular desktop >>> workloads, easily 50% for kernel builds and much more than that (in >>> excess of 100%) for file-read-intense workloads. We cannot just walk >> >> >> And as everybody knows in servers is a popular practice to disable it. >> According to an interview to the kernel.org admins.... >> >> "Beyond that, Peter noted, "very little fancy is going on, and that is >> good >> because fancy is hard to maintain." He explained that the only fancy >> thing >> being done is that all filesystems are mounted noatime meaning that the >> system doesn't have to make writes to the filesystem for files which are >> simply being read, "that cut the load average in half." >> >> I bet that some people would consider such performance hit a bug... >> > > actually, it's popular practice to disable it by people who know how big > a hit it is and know how few programs use it. > > i've been a linux sysadmin for 10 years, and have known about noatime > for at least 7 years, but I always thought of it in the catagory of 'use > it only on your performance critical machines where you are trying to > extract every ounce of performance, and keep an eye out for things > misbehaving' > > I never imagined that itwas the 20%+ hit that is being described, and > with so little impact, or I would have switched to it across the board > years ago. > To get that magnitude you need slow disk with very fast CPU. It helps most of systems where the disk hardware is marginal or worse for the i/o load. Don't take that as typical. > I'll bet there are a lot of admins out there in the same boat. > > adding an option in the kernel to change the default sounds like a very > good first step, even if the default isn't changed today. > -- Bill Davidsen "We have more to fear from the bungling of the incompetent than from the machinations of the wicked." - from Slashdot - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/