From mboxrd@z Thu Jan  1 00:00:00 1970
From: Zhigang Wang <zhigang.x.wang@oracle.com>
Subject: Re: Cpu pools discussion
Date: Wed, 29 Jul 2009 08:29:43 +0800
Message-ID: <4A6F97F7.3080303@oracle.com>
References: <C694DC8E.10D23%keir.fraser@eu.citrix.com>
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To: Keir Fraser <keir.fraser@eu.citrix.com>
Cc: Tim Deegan <Tim.Deegan@eu.citrix.com>, George Dunlap <dunlapg@umich.edu>, Dan Magenheimer <dan.magenheimer@oracle.com>, "xen-devel@lists.xensource.com" <xen-devel@lists.xensource.com>, Juergen Gross <juergen.gross@ts.fujitsu.com>
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Keir Fraser wrote:
> On 28/07/2009 16:29, "Dan Magenheimer" <dan.magenheimer@oracle.com> wrote:
> 
>> Currently this is done with pinning, but pinning
>> does restrict the flexibility of a multi-vcpu VM.
>> Affinity seems like it should help, but affinity
>> doesn't restrict the VM from running on a non-affinitive
>> pcpu (does it?)
> 
> Yes it does. VCPUs only run on PCPUs in their affinity masks.
> 
>  -- Keir
> 
> 
I'm wondering is there some performance difference between these
two scenario:

1) vcpu0 pinned to pcpu0, vcpu1 pinned to pcpu1.
2) vcpu0 and vcpu1 affined to pcpu0 and pcpu1 but not pinned.

Currently we have to explicitly pin *every* vcpu to get true hard partitioning.

We are seeking for a better solution, whether it will be in the hypervisor or just
user space tools. But seems the cpu pool concept is attractive.

thanks,

zhigang