From mboxrd@z Thu Jan  1 00:00:00 1970
From: Avi Kivity <avi@redhat.com>
Subject: Re: [RFC] CPU hard limits
Date: Sun, 07 Jun 2009 09:10:13 +0300
Message-ID: <4A2B59C5.7060902@redhat.com>
References: <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> <4A28B4CE.4010004@redhat.com> <20090605093947.GJ11755@balbir.in.ibm.com> <4A291A2F.3090201@redhat.com> <4A293196.2060006@nortel.com>
Mime-Version: 1.0
Content-Type: text/plain; charset=ISO-8859-1; format=flowed
Content-Transfer-Encoding: 7bit
Cc: balbir@linux.vnet.ibm.com, bharata@linux.vnet.ibm.com,
	linux-kernel@vger.kernel.org,
	Dhaval Giani <dhaval@linux.vnet.ibm.com>,
	Vaidyanathan Srinivasan <svaidy@linux.vnet.ibm.com>,
	Gautham R Shenoy <ego@in.ibm.com>,
	Srivatsa Vaddagiri <vatsa@in.ibm.com>,
	Ingo Molnar <mingo@elte.hu>,
	Peter Zijlstra <a.p.zijlstra@chello.nl>,
	Pavel Emelyanov <xemul@openvz.org>, kvm@vger.kernel.org,
	Linux Containers <containers@lists.linux-foundation.org>,
	Herbert Poetzl <herbert@13thfloor.at>
To: Chris Friesen <cfriesen@nortel.com>
Return-path: <kvm-owner@vger.kernel.org>
Received: from mx2.redhat.com ([66.187.237.31]:57344 "EHLO mx2.redhat.com"
	rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP
	id S1752322AbZFGGL7 (ORCPT <rfc822;kvm@vger.kernel.org>);
	Sun, 7 Jun 2009 02:11:59 -0400
In-Reply-To: <4A293196.2060006@nortel.com>
Sender: kvm-owner@vger.kernel.org
List-ID: <kvm.vger.kernel.org>

Chris Friesen wrote:
> Avi Kivity wrote:
>
>   
>> I am selling virtual private servers.  A 10% cpu share costs $x/month, 
>> and I guarantee you'll get that 10%, or your money back.  On the other 
>> hand, I want to limit cpu usage to that 10% (maybe a little more) so 
>> people don't buy 10% shares and use 100% on my underutilized servers.  
>> If they want 100%, let them pay for 100%.
>>     
>
> What about taking a page from the networking folks and specifying cpu
> like a networking SLA?
>
> Something like "group A is guaranteed X percent (or share) of the cpu,
> but it is allowed to burst up to Y percent for Z milliseconds"
>
> If a rule of this form was the first-class citizen, it would provide
> both guarantees, limits, and flexible behaviour.
>   

I think you're introducing a new control (guarantees, limits, burst 
limit), but I like it.

-- 
Do not meddle in the internals of kernels, for they are subtle and quick to panic.