Reactive NUMA: a design for unifying S-COMA and CC-NUMA

  • Authors:

  • Babak Falsafi;David A. Wood

  • Affiliations:

  • Computer Sciences Department, University of Wisconsin, Madison, 1210 W. Dayton Street, Madison, WI;Computer Sciences Department, University of Wisconsin, Madison, 1210 W. Dayton Street, Madison, WI

  • Venue:
  • Proceedings of the 24th annual international symposium on Computer architecture
  • Year:
  • 1997

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Abstract

This paper proposes and evaluates a new approach to directory-based cache coherence protocols called Reactive NUMA (R-NUMA). An R-NUMA system combines a conventional CC-NUMA coherence protocol with a more-recent Simple-COMA (S-COMA) protocol. What makes R-NUMA novel is the way it dynamically reacts to program and system behavior to switch between CC-NUMA and S-COMA and exploit the best aspects of both protocols. This reactive behavior allows each node in an R-NUMA system to independently choose the best protocol for a particular page, thus providing much greater performance stability than either CC-NUMA or S-COMA alone. Our evaluation is both qualitative and quantitative. We first show the theoretical result that R-NUMA's worst-case performance is bounded within a small constant factor (i.e., two to three times) of the best of CC-NUMA and S-COMA. We then use detailed execution-driven simulation to show that, in practice, R-NUMA usually performs better than either a pure CC-NUMA or pure S-COMA protocol, and no more than 57% worse than the best of CC-NUMA and S-COMA, for our benchmarks and base system assumptions.