Re: [Xen-users] CPU load average above 2 on domU but load average 0 on dom0-XCP 1.6

[Ian Campbell <Ian.Campbell@xxxxxxxxxx>]

On Wed, 2012-11-28 at 16:17 +0000, kevin parker wrote:
> Hi all,
>         I am trying to understand this.I am running XCP 1.6 on a
> machine with 4GB and i5 processor with 3 ubuntu 12.04 64 bit domUs
> each with one vcpu.
> On one of the domU i am having mongodb taking 100% CPU resulting in
> load average of 2.1, 2, 2.But still load average on dom0 is 0, 0, 0.
> If the vcpu is over utilized then why there is no impact on dom0,as
> its load average  is showing 0.

Unless the domU is requiring services from dom0 (i.e. heavy i/o traffic
to a backend based in dom0) there's no reason that domU load average
should have any impact on dom0's (or any other domU) load average.

> on the xentop output i can see all other domU are idle but this
> showing 100% CPU usage.Can any one please explain why this is so?
> If there are 4 cores on dom0 and one of the vm takes 100% CPU then
> doesn't load average  on dom0 should be 1.Can any one please clarify
> me. 

vcpus under Xen separate entities isolated, domU vcpus do not somehow
consume dom0 time.

You are perhaps confusing this with the KVM model where guest vcpus are
actually threads in the host OS (which is equivalent to dom0).

Ian.



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