[Libvir] VCPU mapping into the XML

[Daniel P. Berrange]

On Tue, Feb 27, 2007 at 06:40:54PM +0900, ASANO Yuzuru wrote:
> Hello,
> 
> I want to add the info of VCPU mapping into the XML,
> because we cannot manage VCPU mapping automatically
> when a domain starts or reboots.
> 
> But in the following patch, the function written in "TODO"
> which I wanted has not been accepted.
> 
> https://www.redhat.com/archives/libvir-list/2006-August/msg00015.html
> 
> If I provided the patch managing VCPU mapping in the XML, do you accept it?

The VCPU mapping, schedular parameters, and similar types of data are all 
examples of 'runtime policy' you'd apply to a guest domain. The XML format 
meanwhile, is expressing a guest's virtual hardware definition. IMHO we
should not mix runtime policy with hardware defintiion, and thus I'd say
it was not appropriate to include VCPU mapping in the XML.

Libvirt is really just the lowest level is what I see as a stack of tools
for managing virtual machines. Above libvirt I'd expect to see some form
of 'policy manager' which defines/controls things such as VCPU mapping,
or schedular parameters, and even managing when a VM runs at all. One
simple policy manager might just apply a statically defined VCPU mapping
when a new guest starts up. A more advanced policy manager would collect
resource utilization data, perform some analysis on this data, and thus
apply changes to the VCPU mapping periodically over lifetime of a guest.
Such VM policy management tools can already just use the existing APIs
for setting VCPU mapping.

Anyone with arguments for/against including VCPU info in the XML do feel
free to (dis-)agree with me though...

Regards,
Dan.
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