Re: [Libvir] VCPU mapping into the XML
On Tue, Feb 27, 2007 at 02:07:14PM -0500, 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.
A couple of things
- This doesn't need to be at all related to libvirt release dates,
so if people want to experiment with policy management daemons
it can be done today....
- Expect to throw away the first few versions - policy management
is seriously non-trivial and I doubt anyone will get it right
first time. Better to prototype ideas quickly than to over design
it from the start.
- I expect it'll turn out that there a few different ways to approach
policy, and the idea of a single policy manager may well be impossible.
- There is no good way to collect, distribute & process resource
utilization data at this time - traditional monitoring systems
have all sorts of plugins for collecting data, but once collected
they are typically a black box - no formal API for external apps to
get at the data collected for analysis.
Further thoughts, anyone?
I'd encourage anyone interested in it, to experiment / prototype any
ideas as a project in their own right. The core libvirt APIs needed for
such a system are all there....
Dan.
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