1. A method of assigning virtual memory to physical memory in a data processing system, comprising the steps of: allocating a set of physical memory pages of the data processing system for a new virtual superpage mapping; instructing a memory controller of the data processing system to move a plurality of virtual memory pages corresponding to an old page mapping to the set of physical memory pages corresponding to the new virtual superpage mapping; and accessing at least one of the virtual memory pages using the new virtual superpage mapping while the memory controller is copying old physical memory pages to new physical memory pages.