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[Xen-devel] Re: Too much VCPUS makes domU high CPU utiliazation

To: MaoXiaoyun <tinnycloud@xxxxxxxxxxx>
Subject: [Xen-devel] Re: Too much VCPUS makes domU high CPU utiliazation
From: George Dunlap <george.dunlap@xxxxxxxxxx>
Date: Thu, 19 May 2011 17:21:12 +0100
Cc: George Dunlap <George.Dunlap@xxxxxxxxxxxxx>, xen devel <xen-devel@xxxxxxxxxxxxxxxxxxx>
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This happens only during boot, is that right?  It sounds like maybe
Linux is trying to use some kind of barrier synchronization and failing
because it's having a hard time getting all 16 vcpus to run at once.  If
that's the case, I think it's pretty much a Linux kernel issue; not sure
what the hypervisor can do about it.


On Wed, 2011-05-18 at 17:19 +0100, MaoXiaoyun wrote:
> HI: 
>      I have a host with 16 physical CPUS. Dom0 has 4 VCPUS.
>     When only start a domU-A(windows 2003 x86 64rc 2) with 16 VCPUS,
> it starts quickly and eveything is fine.
>      But if I first start domU-B, which has 2VCPUS, domU-C 4VCPUS, and
> domU-D 8 VCPUS,  later I start DomUA again,
> (so we have total 34 VCPUS, plus dom0), it will takes very long time
> for domU-A to start ,and during the start, its CPU
> utilizaiton is around 800% from xm top, after its start, it response
> very slow in VNC, ans CPU utiliazation keeps high.
> And right after I destoy other 3 domUs, domUA CPU drops to normal.
>    It might relate to CPU schedule, btw, my xen is 4.0.1.
>   Any comments? 

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