From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1945942AbWANBMS (ORCPT ); Fri, 13 Jan 2006 20:12:18 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1423259AbWANBMS (ORCPT ); Fri, 13 Jan 2006 20:12:18 -0500 Received: from e31.co.us.ibm.com ([32.97.110.149]:65453 "EHLO e31.co.us.ibm.com") by vger.kernel.org with ESMTP id S1423248AbWANBMR (ORCPT ); Fri, 13 Jan 2006 20:12:17 -0500 Subject: Fall back io scheduler for 2.6.15? From: Mingming Cao Reply-To: cmm@us.ibm.com To: Andrew Morton Cc: Seetharami Seelam , linux-kernel@vger.kernel.org, ext2-devel@lists.sourceforge.net In-Reply-To: <20060111114303.45540193.akpm@osdl.org> References: <1112673094.14322.10.camel@mindpipe> <1112879303.2859.78.camel@sisko.sctweedie.blueyonder.co.uk> <1112917023.3787.75.camel@dyn318043bld.beaverton.ibm.com> <1112971236.1975.104.camel@sisko.sctweedie.blueyonder.co.uk> <1112983801.10605.32.camel@dyn318043bld.beaverton.ibm.com> <1113220089.2164.52.camel@sisko.sctweedie.blueyonder.co.uk> <1113244710.4413.38.camel@localhost.localdomain> <1113249435.2164.198.camel@sisko.sctweedie.blueyonder.co.uk> <1113288087.4319.49.camel@localhost.localdomain> <1113304715.2404.39.camel@sisko.sctweedie.blueyonder.co.uk> <1113348434.4125.54.camel@dyn318043bld.beaverton.ibm.com> <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> Content-Type: text/plain Organization: IBM LTC Date: Fri, 13 Jan 2006 17:12:15 -0800 Message-Id: <1137201135.4353.81.camel@localhost.localdomain> 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 Wed, 2006-01-11 at 11:43 -0800, Andrew Morton wrote: > Mingming Cao wrote: > > > > # time ./filetst -b 1048576 -w -f /mnt/a > > 2.6.14 2.6.15 > > real 0m21.710s 0m25.773s > > user 0m0.012s 0m0.004s > > sys 0m14.569s 0m15.065s > > That's a big drop. > > Was it doing I/O, or was it all from pagecache? > > > I also found tiobench(sequential write test) and dbench has similar > > regression between 2.6.14 and 2.6.15. Actually I found 2.6.15 rc2 > > already has the regression. Is this a known issue? > > No, it is not known. > > > Anyway I will continue looking at the issue... > > Thanks. Hi, Andrew, I did some trace, it turns out there isn't regression between 2.6.14 and 2.6.15, and there is no problem in ext3 filesystem. I am comparing apple to orange: the tests were run on two different io schedulers. That makes the bogus throughput difference that I reported to you earlier this week. I gave the same boot option "elevator=as" for both 2.6.14 and 2.6.15-rc2 (this has been working for me for a long time to get the anticipatory scheduler on), but the results are, the io schedulers turned on on the two kernels are different( see elevator_setup_default()). 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. 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) ... Thanks, Mingming