1. A method of data processing in a data processing system including a processor core, a multi-level cache memory hierarchy including a lowest level cache, a memory controller, and a system memory, said method comprising: the memory controller determining an addresses of data present in a physical write queue of the memory controller; in response to the determining, the memory controller initiating accesses to the lowest level cache to retrieve into the physical write queue selected cachelines of data having spatial locality with the data present in the physical write queue; and in response to receipt of the selected cachelines of data, the memory controller placing the selected cachelines of data in the physical write queue and thereafter writing the selected cachelines of data to the system memory.