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

To: "Keir Fraser" <keir.fraser@xxxxxxxxxxxxx>, "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: "Tian, Kevin" <kevin.tian@xxxxxxxxx>
Date: Fri, 12 Sep 2008 14:04:24 +0800
Cc: xen-devel@xxxxxxxxxxxxxxxxxxx, "Wei, Gang" <gang.wei@xxxxxxxxx>
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Thread-topic: [Xen-devel] Re: [PATCH 1/4] CPU online/offline support in Xen
>From: Keir Fraser
>Sent: 2008年9月12日 14:02
>To: Tian, Kevin; Shan, Haitao; Haitao Shan
>Cc: xen-devel@xxxxxxxxxxxxxxxxxxx; Wei, Gang
>Subject: Re: [Xen-devel] Re: [PATCH 1/4] CPU online/offline 
>support in Xen
>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 
>approach, beyond a certain point you'll be investing effort 
>for smaller and
>smaller further gains.

Sure I agree, and beyond that point a weak-designed governor
may even slow system with no actual gain.


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