Turn-based Spatiotemporal Coherence for GPUs

Abstract

This article introduces turn-based spatiotemporal coherence. Spatiotemporal coherence is a novel coherence implementation that assigns write permission to epochs (or turns) as opposed to a processor core. This paradigm shift in the assignment of write permissions satisfies all conditions of a coherence protocol with virtually no coherence overhead. We discuss the implementation of this coherence mechanism on a baseline GPU. The evaluation shows that spatiotemporal coherence achieves a speedup of 7.13% for workloads with read data reuse across kernels compared to the baseline software-managed GPU coherence implementation while also providing write atomicity and avoiding the need for software inserted acquire-release operations.¹