Re: Too much VCPUS makes domU high CPU utiliazation

[George Dunlap <george.dunlap@citrix.com>]

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.

 -George

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? 
>  
>