Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1758891AbXHEPCp (ORCPT ); Sun, 5 Aug 2007 11:02:45 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1754958AbXHEPCg (ORCPT ); Sun, 5 Aug 2007 11:02:36 -0400 Received: from thunk.org ([69.25.196.29]:36901 "EHLO thunker.thunk.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754987AbXHEPCe (ORCPT ); Sun, 5 Aug 2007 11:02:34 -0400 Date: Sun, 5 Aug 2007 10:46:45 -0400 From: Theodore Tso To: Alan Cox Cc: Claudio Martins , Jeff Garzik , Ingo Molnar , =?iso-8859-1?Q?J=F6rn?= Engel , 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, david@lang.hm Subject: Re: [PATCH 00/23] per device dirty throttling -v8 Message-ID: <20070805144645.GA28263@thunk.org> Mail-Followup-To: Theodore Tso , Alan Cox , Claudio Martins , Jeff Garzik , Ingo Molnar , =?iso-8859-1?Q?J=F6rn?= Engel , 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, david@lang.hm References: <20070803123712.987126000@chello.nl> <46B4E161.9080100@garzik.org> <20070804224706.617500a0@the-village.bc.nu> <200708050051.40758.ctpm@ist.utl.pt> <20070805014926.400d0608@the-village.bc.nu> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20070805014926.400d0608@the-village.bc.nu> User-Agent: Mutt/1.5.13 (2006-08-11) X-SA-Exim-Connect-IP: X-SA-Exim-Mail-From: tytso@thunk.org X-SA-Exim-Scanned: No (on thunker.thunk.org); SAEximRunCond expanded to false Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1930 Lines: 37 On Sun, Aug 05, 2007 at 01:49:26AM +0100, Alan Cox wrote: > HSM is the usual one, and to a large extent probably why Unix originally > had atime. Basically migrating less used files away so as to keep the > system disks tidy. > > Its not something usally found on desktop boxes so it doesn't in anyway > argue against the distribution using noatime or relative atime, but on > big server boxes it matters In addition, big server boxes are usually not reading a huge *number* of files per second. The place where you see this as a problem is (a) compilation, thanks to huge /usr/include hierarchies (and here things have gotten worse over time as include files have gotten much more complex than in the early Unix days), and (b) silly desktop apps that want to scan huge numbers of XML files or who want to read every single image file on the desktop or in an open file browser window to show c00l icons. Oh, and I guess I should include Maildir setups. If you are always reading from the same small set of files (i.e., a database workload), then those inodes only get updated every 5 seconds (the traditional/default metadata update sync time, as well as the default ext3 journal update time), it's no big deal. Or if you are running a mail server, most of the time the mail queue files are getting updated anyway as you process them, and usually the mail is delivered before 5 seconds is up anyway. So earlier, when Ingo characterized it as, "whenever you read from a file, even one in memory cache.... do a write!", it's probably a bit unfair. Traditional Unix systems simply had very different workload characteristics than many modern dekstop systems today. - Ted - 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/