1. A memory system comprising: a memory controller for implementing memory hierarchy placement decisions, a processor; a processor cache coupled to said memory controller and said processor; a main memory coupled to said memory controller and said processor cache; an in-memory processing element coupled to said main memory and said memory controller; said memory controller selectively routing arriving data directly into said main memory; and said memory controller selectively injecting the data into said processor cache; one of said memory controller and said in-memory processing element, selectively driving placement of the data into a level of the memory hierarchy.