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

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Message-ID: <4A28B539.3050001@redhat.com>
Date:	Fri, 05 Jun 2009 09:03:37 +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:
>> 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.
>
> For your question, if there is a CPU hog running, it would be as per
> the matrix calculation, since the system has no idle point during the
> bandwidth period.
>   

So the groups with guarantees get a priority boost.  That's not a good 
side effect.

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

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