From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751153AbWAPTpi (ORCPT ); Mon, 16 Jan 2006 14:45:38 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1751172AbWAPTpi (ORCPT ); Mon, 16 Jan 2006 14:45:38 -0500 Received: from e33.co.us.ibm.com ([32.97.110.151]:36480 "EHLO e33.co.us.ibm.com") by vger.kernel.org with ESMTP id S1751153AbWAPTpi (ORCPT ); Mon, 16 Jan 2006 14:45:38 -0500 Subject: [PATCH] Fall back io scheduler ( Re: [Ext2-devel] Re: Fall back io scheduler for 2.6.15?) From: Mingming Cao Reply-To: cmm@us.ibm.com To: Jens Axboe Cc: Andrew Morton , seelam@cs.utep.edu, linux-kernel@vger.kernel.org, ext2-devel@lists.sourceforge.net In-Reply-To: <20060116084309.GN3945@suse.de> References: <1113388142.3019.12.camel@sisko.sctweedie.blueyonder.co.uk> <1114207837.7339.50.camel@localhost.localdomain> <1114659912.16933.5.camel@mindpipe> <1114715665.18996.29.camel@localhost.localdomain> <1136935562.4901.41.camel@dyn9047017067.beaverton.ibm.com> <20060110212551.411a766d.akpm@osdl.org> <1137007032.4395.24.camel@localhost.localdomain> <20060111114303.45540193.akpm@osdl.org> <1137201135.4353.81.camel@localhost.localdomain> <20060113174914.7907bf2c.akpm@osdl.org> <20060116084309.GN3945@suse.de> Content-Type: text/plain Organization: IBM LTC Date: Mon, 16 Jan 2006 11:45:35 -0800 Message-Id: <1137440735.3724.17.camel@dyn9047017067.beaverton.ibm.com> Mime-Version: 1.0 X-Mailer: Evolution 2.0.4 (2.0.4-7) Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org On Mon, 2006-01-16 at 09:43 +0100, Jens Axboe wrote: > On Fri, Jan 13 2006, Andrew Morton wrote: > > Mingming Cao wrote: > > > > > > On 2.6.14, the > > > fall back io scheduler (if the chosen io scheduler is not found) is set > > > to the default io scheduler (anticipatory, in this case), but since > > > 2.6.15-rc1, this semanistic is changed to fall back to noop. > > > > OK. And I assume that AS wasn't compiled, so that's why it fell back? > > > > I actually thought that elevator= got removed, now we have > > /sys/block/sda/queue/scheduler. But I guess that's not very useful with > > CONFIG_SYSFS=n. > > > > > Is there any reason to fall back to noop instead of as? It seems > > > anticipatory is much better than noop for ext3 with large sequential > > > write tests (i.e, 1G dd test) ... > > > > I suspect that was an accident. Jens? > > It is, it makes more sense to fallback to the default of course. > How about this one? In the case the chosen io scheduler (elevator = "xxx") is not on the registered list, fall back to default scheduler makes more sense. Signed-off-by: Mingming Cao --- linux-2.6.15-ming/block/elevator.c | 4 ++-- 1 files changed, 2 insertions(+), 2 deletions(-) diff -puN block/elevator.c~default-fall-back-scheduler-fix block/elevator.c --- linux-2.6.15/block/elevator.c~default-fall-back-scheduler-fix 2006-01-16 11:42:04.000446588 -0800 +++ linux-2.6.15-ming/block/elevator.c 2006-01-16 11:42:41.145131615 -0800 @@ -151,12 +151,12 @@ static void elevator_setup_default(void) strcpy(chosen_elevator, CONFIG_DEFAULT_IOSCHED); /* - * If the given scheduler is not available, fall back to no-op. + * If the given scheduler is not available, fall back to default. */ if ((e = elevator_find(chosen_elevator))) elevator_put(e); else - strcpy(chosen_elevator, "noop"); + strcpy(chosen_elevator, CONFIG_DEFAULT_IOSCHED); } static int __init elevator_setup(char *str) _