Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752255AbZFEEuG (ORCPT ); Fri, 5 Jun 2009 00:50:06 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1750876AbZFEEtv (ORCPT ); Fri, 5 Jun 2009 00:49:51 -0400 Received: from e6.ny.us.ibm.com ([32.97.182.146]:41361 "EHLO e6.ny.us.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750783AbZFEEtv (ORCPT ); Fri, 5 Jun 2009 00:49:51 -0400 Date: Fri, 5 Jun 2009 12:49:46 +0800 From: Balbir Singh To: Avi Kivity 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 , kvm@vger.kernel.org, Linux Containers , Herbert Poetzl Subject: Re: [RFC] CPU hard limits Message-ID: <20090605044946.GA11755@balbir.in.ibm.com> Reply-To: balbir@linux.vnet.ibm.com References: <20090604053649.GA3701@in.ibm.com> <4A27BBCA.5020606@redhat.com> <20090605030309.GA3872@in.ibm.com> <4A28921C.6010802@redhat.com> <661de9470906042137u603e2997n80c270bf7f6191ad@mail.gmail.com> <4A28A2AB.3060108@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline In-Reply-To: <4A28A2AB.3060108@redhat.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: 2655 Lines: 75 * Avi Kivity [2009-06-05 07:44:27]: > Balbir Singh wrote: >> On Fri, Jun 5, 2009 at 11:33 AM, Avi Kivity wrote: >> >>> Bharata B Rao wrote: >>> >>>>> Another way is to place the 8 groups in a container group, and limit >>>>> that to 80%. But that doesn't work if I want to provide guarantees to >>>>> several groups. >>>>> >>>>> >>>> Hmm why not ? Reduce the guarantee of the container group and provide >>>> the same to additional groups ? >>>> >>>> >>> This method produces suboptimal results: >>> >>> $ cgroup-limits 10 10 0 >>> [50.0, 50.0, 40.0] >>> >>> I want to provide two 10% guaranteed groups and one best-effort group. >>> Using the limits method, no group can now use more than 50% of the >>> resources. However, having the first group use 90% of the resources does >>> not violate any guarantees, but it not allowed by the solution. >>> >>> >> >> How, it works out fine in my calculation >> >> 50 + 40 for G2 and G3, make sure that G1 gets 10%, since others are >> limited to 90% >> 50 + 40 for G1 and G3, make sure that G2 gets 10%, since others are >> limited to 90% >> 50 + 50 for G1 and G2, make sure that G3 gets 0%, since others are >> limited to 100% >> > > It's fine in that it satisfies the guarantees, but it is deeply > suboptimal. If I ran a cpu hog in the first group, while the other two > were idle, it would be limited to 50% cpu. On the other hand, if it > consumed all 100% cpu it would still satisfy the guarantees (as the > other groups are idle). > > The result is that in such a situation, wall clock time would double > even though cpu resources are available. But then there is no other way to make a *guarantee*, guarantees come at a cost of idling resources, no? Can you show me any other combination that will provide the guarantee and without idling the system for the specified guarantees? >> Now if we really have zeros, I would recommend using >> >> cgroup-limits 10 10 and you'll see that you'll get 90, 90 as output. >> >> Adding zeros to the calcuation is not recommended. Does that help? > > What do you mean, it is not recommended? I have two groups which need at > least 10% and one which does not need any guarantee, how do I express it? > Ignore this part of my comment > In any case, changing the zero to 1% does not materially change the results. True. -- 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/