Microsoft Corporation
Tracking repeated reads to guide dynamic selection of cache coherence protocols in processor-based devices

Abstract:

Tracking repeated reads to guide dynamic selection of cache coherence protocols in processor-based devices is disclosed. In this regard, a processor-based device includes processing elements (PEs) and a central ordering point circuit (COP). The COP dynamically selects, on a store-by-store basis, either a write invalidate protocol or a write update protocol as a cache coherence protocol to use for maintaining cache coherency for a memory store operation. The COP's selection is based on protocol preference indicators generated by the PEs using repeat-read indicators that each PE maintains to track whether a coherence granule was repeatedly read by the PE (e.g., as a result of polling reads, or as a result of re-reading the coherence granule after it was evicted from a cache due to an invalidating snoop). After selecting the cache coherence protocol, the COP sends a response message to the PEs indicating the selected cache coherence protocol.