From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756370AbYFZXBr (ORCPT ); Thu, 26 Jun 2008 19:01:47 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1751626AbYFZXBi (ORCPT ); Thu, 26 Jun 2008 19:01:38 -0400 Received: from smtp1.linux-foundation.org ([140.211.169.13]:38772 "EHLO smtp1.linux-foundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751239AbYFZXBh (ORCPT ); Thu, 26 Jun 2008 19:01:37 -0400 Date: Thu, 26 Jun 2008 15:59:48 -0700 From: Andrew Morton To: righi.andrea@gmail.com Cc: balbir@linux.vnet.ibm.com, menage@google.com, chlunde@ping.uio.no, axboe@kernel.dk, matt@bluehost.com, roberto@unbit.it, randy.dunlap@oracle.com, dpshah@google.com, containers@lists.linux-foundation.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH 2/3] i/o bandwidth controller infrastructure Message-Id: <20080626155948.34f30751.akpm@linux-foundation.org> In-Reply-To: <486419FE.6070600@gmail.com> References: <1213956335-29866-3-git-send-email-righi.andrea@gmail.com> <20080625172900.6cfe79cf.akpm@linux-foundation.org> <486419FE.6070600@gmail.com> X-Mailer: Sylpheed version 2.2.4 (GTK+ 2.8.20; i486-pc-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, 27 Jun 2008 00:36:46 +0200 Andrea Righi wrote: > > Does all this code treat /dev/sda1 as a separate device from /dev/sda2? > > If so, that would be broken. > > Yes, all the partitions are treated as separate devices with > (potentially) different limiting rules, but I don't understand why it > would be broken... dev_t has both minor and major numbers, so it would > be possible to select single partitions as well. Well it's functionally broken, isn't it? A physical disk has a fixed IO bandwidth and when the administrator wants to partition that bandwidth amongst control groups he will need to consider the entire device when doing so? I mean, the whole point of this feature and of control groups as a whole is isolation. But /dev/sda1 and /dev/sda2 are very much _not_ isolated. Whereas /dev/sda and /dev/sdb are (to a large degree) isolated.