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Re: [Xen-devel] Re: [PATCH 1/4] CPU online/offline support in Xen

To: "Tian, Kevin" <kevin.tian@xxxxxxxxx>, "Shan, Haitao" <haitao.shan@xxxxxxxxx>, Haitao Shan <maillists.shan@xxxxxxxxx>
Subject: Re: [Xen-devel] Re: [PATCH 1/4] CPU online/offline support in Xen
From: Keir Fraser <keir.fraser@xxxxxxxxxxxxx>
Date: Fri, 12 Sep 2008 07:02:27 +0100
Cc: xen-devel@xxxxxxxxxxxxxxxxxxx, "Wei, Gang" <gang.wei@xxxxxxxxx>
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On 12/9/08 03:22, "Tian, Kevin" <kevin.tian@xxxxxxxxx> wrote:

>> I consider this might be a nice win for possibly less effort than is
> being
>> expended in trying to make idle residency times (and hence Cx
> residency
>> times) as long as possible.
> These two don't conflict. Cpu online/offline can't be used in small
> interval due
> to long latency and added overhead to whole system, but it makes sense
> when administrator realizes low cpu utilization in a relatively long
> period like
> in hrs. Current idle governor instead runs in fine-grained level to fit
> the otherwise
> cases.

I certainly agree with that. Just pointing out that, with the fine-graiend
approach, beyond a certain point you'll be investing effort for smaller and
smaller further gains.

 -- Keir

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