Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753841AbZFEGDs (ORCPT ); Fri, 5 Jun 2009 02:03:48 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1750813AbZFEGDj (ORCPT ); Fri, 5 Jun 2009 02:03:39 -0400 Received: from mx2.redhat.com ([66.187.237.31]:45182 "EHLO mx2.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750701AbZFEGDi (ORCPT ); Fri, 5 Jun 2009 02:03:38 -0400 Message-ID: <4A28B4CE.4010004@redhat.com> Date: Fri, 05 Jun 2009 09:01:50 +0300 From: Avi Kivity User-Agent: Thunderbird 2.0.0.21 (X11/20090320) MIME-Version: 1.0 To: bharata@linux.vnet.ibm.com CC: Balbir Singh , 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 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> <20090605044946.GA11755@balbir.in.ibm.com> <20090605051050.GB11755@balbir.in.ibm.com> <4A28AB67.7040800@redhat.com> <20090605052755.GE11755@balbir.in.ibm.com> <20090605053159.GB3872@in.ibm.com> In-Reply-To: <20090605053159.GB3872@in.ibm.com> Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2118 Lines: 51 Bharata B Rao wrote: > On Fri, Jun 05, 2009 at 01:27:55PM +0800, Balbir Singh wrote: > >> * Avi Kivity [2009-06-05 08:21:43]: >> >> >>> Balbir Singh wrote: >>> >>>>> 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? >>>>> >>>>> >>>> OK, I see part of your concern, but I think we could do some >>>> optimizations during design. For example if all groups have reached >>>> their hard-limit and the system is idle, should we do start a new hard >>>> limit interval and restart, so that idleness can be removed. Would >>>> that be an acceptable design point? >>>> >>> I think so. Given guarantees G1..Gn (0 <= Gi <= 1; sum(Gi) <= 1), and a >>> cpu hog running in each group, how would the algorithm divide resources? >>> >>> >> As per the matrix calculation, but as soon as we reach an idle point, >> we redistribute the b/w and start a new quantum so to speak, where all >> groups are charged up to their hard limits. >> > > But could there be client models where you are required to strictly > adhere to the limit within the bandwidth and not provide more (by advancing > the bandwidth period) in the presence of idle cycles ? > That's the limit part. I'd like to be able to specify limits and guarantees on the same host and for the same groups; I don't think that works when you advance the bandwidth period. I think we need to treat guarantees as first-class goals, not something derived from limits (in fact I think guarantees are more useful as they can be used to provide SLAs). -- I have a truly marvellous patch that fixes the bug which this signature is too narrow to contain. -- 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/