A processing unit for a data processing system includes a processor core having one or more execution units for processing instructions and a register file for storing data accessed in processing of the instructions. The processing unit also includes a multi-level cache hierarchy coupled to and supporting the processor core. The multi-level cache hierarchy includes at least one upper level of cache memory having a lower access latency and at least one lower level of cache memory having a higher access latency. The lower level of cache memory, responsive to receipt of a memory access request that hits only a partial cache line in the lower level cache memory, sources the partial cache line to the at least one upper level cache memory to service the memory access request. The at least one upper level cache memory services the memory access request without caching the partial cache line.