Measuring flexibility in single-ISA heterogeneous processors

Single-ISA heterogeneous processors are a promising method for enabling runtime power flexibility. Low-priority programs run on low-power cores, and high-priority programs run on high-power cores. In recent years, a number of methods for heterogeneous design space exploration have emerged. These methods search the design space for Pareto frontiers of cores that are optimal for power and speed. We demonstrate that a heterogeneous processor cannot be composed by simply selecting some cores from a Pareto-optimal set; the selection must give even coverage of the design space. We then define a metric — clumpiness — for measuring how well selected heterogeneous cores cover the design space.