A study on performance benefits of core morphing in an asymmetric multicore processor

Multicore architectures are designed so as to provide an acceptable level of performance per unit power for the majority of applications. Consequently, we must occasionally expect applications that could have benefited from a more powerful core in terms of either lower execution time and/or lower energy consumed. Fusing some of the resources of two (or more) cores to configure a more powerful core for such instances is a natural approach to deal with those few applications that have very high performance demands. However, a recent study has shown that fusing homogeneous cores is unlikely to benefit applications. In this paper we study the potential performance benefits of core morphing in a heterogeneous multicore processor that can be reconfigured at runtime. We consider as an example a dual core processor with one of the two cores being designed to target integer intensive applications while the other is better suited to floating-point intensive applications. These two cores can be fused into a single powerful core when an application that can benefit from such fusion is executing. We first discuss the design principles of the two individual cores so that the majority of the benchmarks that we consider execute in a satisfactory way. We then show that a small subset of the considered applications can greatly benefit from core morphing even in the case where two applications that could have been executed in parallel on the two cores are run, for some percentage of time, on the single morphed core. Our results indicate that a performance gain of up to 100% is achievable at a small hardware overhead of less than 1%.