Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752406AbZFEJ47 (ORCPT ); Fri, 5 Jun 2009 05:56:59 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1750984AbZFEJ4u (ORCPT ); Fri, 5 Jun 2009 05:56:50 -0400 Received: from e35.co.us.ibm.com ([32.97.110.153]:60193 "EHLO e35.co.us.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752008AbZFEJzu (ORCPT ); Fri, 5 Jun 2009 05:55:50 -0400 Date: Fri, 5 Jun 2009 17:55:27 +0800 From: Balbir Singh To: Paul Menage Cc: bharata@linux.vnet.ibm.com, linux-kernel@vger.kernel.org, Dhaval Giani , Vaidyanathan Srinivasan , Gautham R Shenoy , Srivatsa Vaddagiri , Ingo Molnar , Peter Zijlstra , Pavel Emelyanov , Avi Kivity , kvm@vger.kernel.org, Linux Containers , Herbert Poetzl Subject: Re: [RFC] CPU hard limits Message-ID: <20090605095527.GM11755@balbir.in.ibm.com> Reply-To: balbir@linux.vnet.ibm.com References: <20090604053649.GA3701@in.ibm.com> <6599ad830906050153i1afd104fqe70f681317349142@mail.gmail.com> <20090605093625.GI11755@balbir.in.ibm.com> <6599ad830906050248m2c569e5bx44fb3bbddf46f8b1@mail.gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline In-Reply-To: <6599ad830906050248m2c569e5bx44fb3bbddf46f8b1@mail.gmail.com> User-Agent: Mutt/1.5.18 (2008-05-17) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2103 Lines: 47 * menage@google.com [2009-06-05 02:48:36]: > On Fri, Jun 5, 2009 at 2:36 AM, Balbir Singh wrote: > > > > The important scenario I have is adding and removing groups. > > > > Consider 10 cgroups with shares of 10 each, what if 5 new are created > > with the same shares? We now start getting 100/15, even though we did > > not change our shares. > > Are you assuming that arbitrary users can create new cgroups whenever > they like, with whatever shares they like? In that situation, how > would you use hard limits to provide guarantees? Presumably if the > user could create a cgroup with an arbitrary share, they could create > one with an arbitrary hard limit too. > What about applications running as root, that can create their own groups? How about multiple instances of the same application started? Do applications need to know that creating a group will hurt guarantees provided to others? > Can you explain a bit more about how you're envisaging cgroups being > created, and how their shares and hard limits would get set? I was > working on the assumption that (for any sub-tree of the CFS hierarchy) > there's a single managing entity that gets to decide the shares given > to the cgroups within that tree. That managing entity would be > responsible for ensuring that the shares given out allowed guarantees > to be met (or alternatively, that the probability of violating those > guarantees based on the shares given out was within some tolerance > threshold). > The point is that there is no single control entity for creating groups. if run a solution, it might create groups without telling the user. No one is arbitrating, not even libcgroup. What if someone changes the cpuset assignment and moves CPUS x to y in an exclusive cpuset all of a sudden. How do we arbitrate? -- Balbir -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/