From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751410AbWGXQd3 (ORCPT ); Mon, 24 Jul 2006 12:33:29 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1751407AbWGXQd3 (ORCPT ); Mon, 24 Jul 2006 12:33:29 -0400 Received: from pentafluge.infradead.org ([213.146.154.40]:2954 "EHLO pentafluge.infradead.org") by vger.kernel.org with ESMTP id S1751405AbWGXQd2 (ORCPT ); Mon, 24 Jul 2006 12:33:28 -0400 Subject: Re: CFQ will be the new default IO scheduler - why? From: Arjan van de Ven To: Al Boldi Cc: linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org In-Reply-To: <200607241857.43399.a1426z@gawab.com> References: <200607241857.43399.a1426z@gawab.com> Content-Type: text/plain Organization: Intel International BV Date: Mon, 24 Jul 2006 18:33:26 +0200 Message-Id: <1153758806.3043.55.camel@laptopd505.fenrus.org> Mime-Version: 1.0 X-Mailer: Evolution 2.2.3 (2.2.3-2.fc4) Content-Transfer-Encoding: 7bit X-SRS-Rewrite: SMTP reverse-path rewritten from by pentafluge.infradead.org See http://www.infradead.org/rpr.html Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org > > Should there be a default scheduler per filesystem? As some filesystems > > may perform better/worse with one over another? > > It's currently perDevice, and should probably be extended to perMount. Hi, per mount is going to be "not funny". I assume the situation you are aiming for is the "3 partitions on a disk, each wants its own elevator". The way the kernel currently works is that IO requests the filesystem does are first flattened into an IO for the entire device (eg the partition mapping is done) and THEN the IO scheduler gets involved to schedule the IO on a per disk basis. The 2.4 kernel did this the other way around, and it was really a bad idea (no fairness, less optimal scheduling all around due to less visibility into what the disk is really doing, several hardware properties such as TCQ depth that affect scheduling IOs are truely per disk not per partition etc etc) So I don't think it's likely that per mount is really an option right now.. Greetings, Arjan van de Ven -- if you want to mail me at work, send mail to arjan (at) linux.intel.com