From mboxrd@z Thu Jan 1 00:00:00 1970 Message-ID: <46BBE3DD.2090209@tmr.com> Date: Fri, 10 Aug 2007 00:04:45 -0400 From: Bill Davidsen MIME-Version: 1.0 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: owner-linux-mm@kvack.org Return-Path: 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 List-ID: david@lang.hm wrote: > On Sun, 5 Aug 2007, Diego Calleja wrote: > >> El Sun, 5 Aug 2007 09:13:20 +0200, Ingo Molnar escribio: >> >>> 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, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org