From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S262007AbULHCUd (ORCPT ); Tue, 7 Dec 2004 21:20:33 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S262009AbULHCUd (ORCPT ); Tue, 7 Dec 2004 21:20:33 -0500 Received: from mail-relay-2.tiscali.it ([213.205.33.42]:63192 "EHLO mail-relay-2.tiscali.it") by vger.kernel.org with ESMTP id S262007AbULHCUZ (ORCPT ); Tue, 7 Dec 2004 21:20:25 -0500 Date: Wed, 8 Dec 2004 03:20:20 +0100 From: Andrea Arcangeli To: Andrew Morton Cc: nickpiggin@yahoo.com.au, axboe@suse.de, linux-kernel@vger.kernel.org Subject: Re: Time sliced CFQ io scheduler Message-ID: <20041208022020.GH16322@dualathlon.random> References: <20041202130457.GC10458@suse.de> <20041202134801.GE10458@suse.de> <20041202114836.6b2e8d3f.akpm@osdl.org> <20041202195232.GA26695@suse.de> <20041208003736.GD16322@dualathlon.random> <1102467253.8095.10.camel@npiggin-nld.site> <20041208013732.GF16322@dualathlon.random> <20041207180033.6699425b.akpm@osdl.org> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20041207180033.6699425b.akpm@osdl.org> X-GPG-Key: 1024D/68B9CB43 13D9 8355 295F 4823 7C49 C012 DFA1 686E 68B9 CB43 X-PGP-Key: 1024R/CB4660B9 CC A0 71 81 F4 A0 63 AC C0 4B 81 1D 8C 15 C8 E5 User-Agent: Mutt/1.5.6i Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Dec 07, 2004 at 06:00:33PM -0800, Andrew Morton wrote: > untuned SCSI benchmark results without realising that. If a distro is > always selecting CFQ then they've probably gone and deoptimised all their > IDE users. The enterprise distro definitely shouldn't use "as" by default: database apps _must_ not use AS, they've to use either CFQ or deadline. CFQ is definitely the best for enterprise distros. This is a tangible result, SCSI/IDE doesn't matter at all (and keep in mind they use O_DIRECT a lot, so such 64kib Jens found would be a showstopper for a enterprise release, slelecting something different than "as" is a _must_ for enterprise distro). In the desktop distro you'll notice the /proc/cmdline has elevator="as" because for desktop distros more people is going to use them for desktop as expected. But for enterprise distros this isn't the case, and cfq (or deadline) must be the default, sure not "as". So claiming that selecting cfq by default (I said in the enterprise distro) is deoptimising users, is a wrong statement and the opposite of reality. And personally I use cfq even on the desktop (since I'm not a normal desktop user and I've apps writing too). > AS needs another iteration of development to fix these things. Right now > it's probably the case that we need CFQ or deadline for servers and AS for > desktops. That's awkward. Exactly. If you believe AS is going to perform better than CFQ on the database enterprise usage, we just need to prove it in practice after the round of fixes, then changing the default back to "as" it'll be an additional one liner on top of the blocker direct-io bug. Desktop is already forced to "as" by /proc/cmdline, so it's not affected on how we change the default of the enterprise distro AFIK.