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Re: [Libvir] VCPU mapping into the XML

ASANO Yuzuru wrote:
Hugh Brock wrote:
Daniel P. Berrange wrote:
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.

I'd be very excited if we could get to a first cut of a simple policy
manager in the fedora 8 timeframe. At a minimum, I would think such a
thing would need to be able to do the following:

1. Store policy information about a guest. At a minimum we would want to
store cpu pin/weight/cap information; beyond that, dependency
information (don't start me until some other VM is up and running).

2. Retrieve policy information on request. So for example we might want
to tell libvirt to ask the manager for policy information before
starting a guest, or before shutting one down.

Just these features would be great for a first cut. Then going forward,
we could start thinking about receiving monitoring information and
responding to events. The tricky thing, it seems to me, is going to be
designing the thing in such a way that it won't take forever to
implement the simple part now, but can still be extended to do more later.

The features I would want to implement now is essentially included in the
above mentioned contents. More correctly, I would particularly want to
implement the following 3 features.

- New domain started by libvirt is set the policy information
    (cpu pin/weight/cap) by policy manager.
- A domain rebooted by libvirt keeps configuration of policy information.
- Some domains can use specified pCPUs by occupancy and the other domains
    are configured not able to use the pCPUs by policy manager.

Are these proposed futures enough for your first step?
If you agreed, I will start design & implementation.

Yuzuru Asano.

I think this is a good place to start. As Dan says in another email, we may wind up doing many implementations of this idea before we get it right. Once you have a design in mind, post it here for comments if you would. Thanks!


Red Hat Virtualization Group http://redhat.com/virtualization
Hugh Brock           | virt-manager http://virt-manager.org
hbrock redhat com    | virtualization library http://libvirt.org

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