Energy-efficient MESI cache coherence with pro-active snoop filtering for multicore microprocessors

We present a snoop filtering mechanism for multicore microprocessors that implement coherent caches using the MESI protocol. The relatively small filter structure at each core maintains coarse-grain sharing information about regions within a page to filter out snoops. On broadcast, the sharing status of all regions within the page is collected proactively and up to 90% of unnecessary snoops are eliminated. The energy savings resulting from snoop filtering in our scheme average about 30% across the benchmarks studied for both a quad core design in 65 nm and 8-core design in 45 nm CMOS.