linux-kernel - Re: [RFC] CPU hard limits

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Message-ID: <4A28AB67.7040800@redhat.com>
Date:	Fri, 05 Jun 2009 08:21:43 +0300
From:	Avi Kivity <avi@...hat.com>
To:	balbir@...ux.vnet.ibm.com
CC:	bharata@...ux.vnet.ibm.com, linux-kernel@...r.kernel.org,
	Dhaval Giani <dhaval@...ux.vnet.ibm.com>,
	Vaidyanathan Srinivasan <svaidy@...ux.vnet.ibm.com>,
	Gautham R Shenoy <ego@...ibm.com>,
	Srivatsa Vaddagiri <vatsa@...ibm.com>,
	Ingo Molnar <mingo@...e.hu>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	Pavel Emelyanov <xemul@...nvz.org>, kvm@...r.kernel.org,
	Linux Containers <containers@...ts.linux-foundation.org>,
	Herbert Poetzl <herbert@...hfloor.at>
Subject: Re: [RFC] CPU hard limits

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?

-- 
I have a truly marvellous patch that fixes the bug which this
signature is too narrow to contain.

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