Coarse-Grain Coherence Tracking: RegionScout and Region Coherence Arrays

Cache-coherent shared-memory multiprocessors have wide-ranging applications, from commercial transaction processing and database services to large-scale scientific computing. Coarse-grain coherence tracking (CGCT) is a new technique that extends a conventional coherence mechanism and optimizes coherence enforcement. It monitors the coherence status of large regions of memory and uses that information to avoid unnecessary broadcasts and filter unnecessary cache tag lookups, thus improving system performance and power consumption. This article presents two CGCT implementations, RegionScout and Region Coherence Arrays, and provides simulation results for a broadcast-based multiprocessor system running commercial, scientific, and multiprogrammed workloads