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

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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