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Achieving Predictable Performance through Better Memory Controller Placement in Many-Core CMPs

Dennis Abts
Natalie Engright Jerger
John Kim
Mikko Lipasti
Proceedings of the International Symposium on Computer Architecture, ACM (2009)


In the near term, Moore's law will continue to provide an increasing number of transistors and therefore an increasing number of on-chip cores. Limited pin bandwidth prevents the integration of a large number of memory controllers on-chip. With many cores, and few memory controllers, where to locate the memory controllers in the on-chip interconnection fabric becomes an important and as yet unexplored question. In this paper, we show how the location of the memory controllers can reduce contention (hot spots) in the on-chip fabric, as well as lower the variance in reference latency which provides for predictable performance of memory-intensive applications regardless of the processing core on which a thread is scheduled. We explore the design space of on-chip fabrics to find optimal memory controller placement relative to different topologies (i.e. mesh and torus), routing algorithms, and workloads.