From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S261978AbULHAzJ (ORCPT ); Tue, 7 Dec 2004 19:55:09 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S261976AbULHAzJ (ORCPT ); Tue, 7 Dec 2004 19:55:09 -0500 Received: from smtp111.mail.sc5.yahoo.com ([66.163.170.9]:53888 "HELO smtp111.mail.sc5.yahoo.com") by vger.kernel.org with SMTP id S261977AbULHAzD (ORCPT ); Tue, 7 Dec 2004 19:55:03 -0500 Subject: Re: Time sliced CFQ io scheduler From: Nick Piggin To: Andrea Arcangeli Cc: Jens Axboe , Andrew Morton , linux-kernel@vger.kernel.org In-Reply-To: <20041208003736.GD16322@dualathlon.random> References: <20041202130457.GC10458@suse.de> <20041202134801.GE10458@suse.de> <20041202114836.6b2e8d3f.akpm@osdl.org> <20041202195232.GA26695@suse.de> <20041208003736.GD16322@dualathlon.random> Content-Type: text/plain Date: Wed, 08 Dec 2004 11:54:13 +1100 Message-Id: <1102467253.8095.10.camel@npiggin-nld.site> Mime-Version: 1.0 X-Mailer: Evolution 2.0.1 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org On Wed, 2004-12-08 at 01:37 +0100, Andrea Arcangeli wrote: > On Thu, Dec 02, 2004 at 08:52:36PM +0100, Jens Axboe wrote: > > with its default io scheduler has basically zero write performance in > > IMHO the default io scheduler should be changed to cfq. as is all but > general purpose so it's a mistake to leave it the default (plus as Jens I think it is actually pretty good at general purpose stuff. For example, the old writes starve reads thing. It is especially bad when doing small dependent reads like `find | xargs grep`. (Although CFQ is probably better at this than deadline too). It also tends to degrade more gracefully under memory load because it doesn't require much readahead. > found the write bandwidth is not existent during reads, no surprise it > falls apart in any database load). We had to make the cfq the default > for the enterprise release already. The first thing I do is to add > elevator=cfq on a new install. I really like how well cfq has been > designed, implemented and turned, Jens's results with his last patch are > quite impressive. > That is synch write bandwidth. Yes that seems to be a problem.