US Patent 8631131 Virtual machine pool cache

A host controller initiates a virtual machine pool, the virtual machine pool including a plurality of stateless virtual machines. The host controller identifies a virtual machine pool cache size value for the virtual machine pool, the virtual machine pool cache size value indicating a number of active, unassigned, stateless virtual machines to maintain in a virtual machine pool cache for the virtual machine pool. The host controller automatically loads the indicated number of active, unassigned, stateless virtual machines into the virtual machine pool cache for the virtual machine pool prior to receiving a request for one of the plurality of stateless virtual machines.