CPU constraints

[Martin Packman]

What do juju users want from a cpu constraint on instances?

I'm adding support in MaaS, and have some choices on what the number
means exactly.

<http://docs.openstack.org/api/openstack-compute/2/content/Get_Flavor_Details-d1e4317.html>

For OpenStack, 'vcpus' is used, which (though not clearly documented?)
is the number of cores the instance has.

<http://aws.amazon.com/ec2/instance-types/>

In EC2 abstract 'compute units' are used, which they correspond
approximately to 1.0-1.2 GHz processors from 2007. However, the
documentation pushes you towards benchmarking on different instance
types over than treating these numbers too seriously.

So, either presenting the number of cpus, or the total GHz, seem like
reasonable options. Which would you find more useful in general? Using
tags in MaaS can constrain on more precise details regardless.

Martin