Feature: CPU/Memory OverCommit

Background: CloudStack performs CPU over-provisioning based on an over-provisioning ratio configured by the administrator. This is defined by the cpu.overprovisioning.factor global configuration variable. Service offerings limits (e.g. 1 GHz, 1 core) are strictly enforced for core count. For example, a guest with a service offering of one core will have only one core available to it regardless of other activity on the Host. Service offering limits for gigahertz are enforced only in the presence of contention for CPU resources. For example, suppose that a guest was created with a service offering of 1 GHz on a Host that has 2 GHz cores, and that guest is the only guest running on the Host. The guest will have the full 2 GHz available to it. When multiple guests are attempting to use the CPU a weighting factor is used to schedule CPU resources. The weight is based on the clock speed in the service offering. Guests receive a CPU allocation that is proportionate to the GHz in the service offering. For example, a guest created from a 2 GHz service offering will receive twice the CPU allocation as a guest created from a 1 GHz service offering.  Currently, CloudStack does not perform memory over-provisioning. 

Requirements:

-          Able to specify memory overcommit ratio

-          Able to specify cpu and memory overcommit on a per-cluster basis