From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755933AbYIDXEE (ORCPT ); Thu, 4 Sep 2008 19:04:04 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1754039AbYIDXDx (ORCPT ); Thu, 4 Sep 2008 19:03:53 -0400 Received: from smtp-out.google.com ([216.239.33.17]:44685 "EHLO smtp-out.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753541AbYIDXDw (ORCPT ); Thu, 4 Sep 2008 19:03:52 -0400 DomainKey-Signature: a=rsa-sha1; s=beta; d=google.com; c=nofws; q=dns; h=message-id:date:from:to:subject:cc:in-reply-to: mime-version:content-type:content-transfer-encoding: content-disposition:references; b=YYppox1JY4C2xlzahfUOFVvGhznDx4WjPf5JrdS4JUVaPgKOhv7Xl05YPc+ktTb0k 3XWMud7erMSGrpuS1ET0g== Message-ID: <6599ad830809041603t320a15eakdfbc6fcab232aa59@mail.gmail.com> Date: Thu, 4 Sep 2008 16:03:43 -0700 From: "Paul Menage" To: "Dhaval Giani" Subject: Re: Default values for cpuset.mems, cpus for children created Cc: pj@sgi.com, danms@us.ibm.com, "Balbir Singh" , lkml , libcg-devel In-Reply-To: <20080815193132.GE11844@linux.vnet.ibm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Content-Disposition: inline References: <20080815193132.GE11844@linux.vnet.ibm.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, Aug 15, 2008 at 12:31 PM, Dhaval Giani wrote: > Now an application programmer does not really care where and how > subsystems are mounted (or at least that is what libcgroup aims to > achieve :-) ). And such a scenario when the cpuset has not been handled > is going to lead to failures which a user is not expecting. > > To work around this, I am making a change which will just set the values > which the parent group has for unfilled values, but I can already see > cpuset breaking that assumption as well. (for example exclusive > cpusets). Yes, this is an awkwardness with the cpusets model of recursively sharing a set of identifiable resources. Quite apart from the backwards compatibility issue, if you make new cpusets inherit their parent's resources you break the exclusive setting, and if you don't you require special setup before the cgroup can be used. There's already a precedent in the cpuset_clone() function, which does inherit the parent's resources, but I don't think the clone behaviour is widely used, and even that doesn't handle the case of exclusive siblings. I'm inclined to say that this is a userspace bug - if you don't want cpusets attached to your cgroup hierarchy, don't include them in the set of mounted subsystems. Paul