From mboxrd@z Thu Jan 1 00:00:00 1970 From: Pavel Emelyanov Subject: Re: [RFC] CPU hard limits Date: Mon, 08 Jun 2009 12:50:51 +0400 Message-ID: <4A2CD0EB.5080900@openvz.org> References: <20090604053649.GA3701@in.ibm.com> <6599ad830906050153i1afd104fqe70f681317349142@mail.gmail.com> <20090605092733.GA27486@in.ibm.com> <6599ad830906050232n11aa30d8xfcda0a279a482f32@mail.gmail.com> <20090605094811.GD4601@linux.vnet.ibm.com> <6599ad830906050251h18f4e037h182f61aa80a5b046@mail.gmail.com> <20090605095931.GE4601@linux.vnet.ibm.com> <6599ad830906050303r404c325anc60ded4f45a50b95@mail.gmail.com> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Cc: Dhaval Giani , bharata@linux.vnet.ibm.com, linux-kernel@vger.kernel.org, Balbir Singh , Vaidyanathan Srinivasan , Gautham R Shenoy , Srivatsa Vaddagiri , Ingo Molnar , Peter Zijlstra , Avi Kivity , kvm@vger.kernel.org, Linux Containers , Herbert Poetzl To: Paul Menage Return-path: Received: from mailhub.sw.ru ([195.214.232.25]:15825 "EHLO relay.sw.ru" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752455AbZFHIvB (ORCPT ); Mon, 8 Jun 2009 04:51:01 -0400 In-Reply-To: <6599ad830906050303r404c325anc60ded4f45a50b95@mail.gmail.com> Sender: kvm-owner@vger.kernel.org List-ID: Paul Menage wrote: > On Fri, Jun 5, 2009 at 2:59 AM, Dhaval Giani wrote: >> I think we are focusing on the wrong use case here. Guarantees is just a >> useful side-effect we get by using hard limits. I think the more >> important use case is where the provider wants to limit the amount of >> time a user gets (such as in a cloud). >> >> Maybe we should direct our attention in solving that problem? :) >> > > Yes, that case and the "predictable load test behaviour" case are both > good reasons for hard limits. ACK. I'd like to add two things. First, the article @openvz.org about guarantees you were discussing was not supposed to be a "best practices" paper. This was just a theoretical thoughts on how to get guarantees out of the limit for those resources you cannot reclaim from the user and thus cannot provide the guarantee any other way. E.g. locked memory - once a user has it you cannot take it back, and if you want to guarantee some mount of it for group X you have to keep all the other groups away from this amount. And the second thing is an addition for Dhaval's case about limiting the amount of time a user gets. This is exactly what hosting providers do - they _sell_ the CPU power to their customers and thus need to limit the CPU time dedicated for containers. > Paul >