Microsoft Technology Licensing, LLC

Derek Bachand

Eric Francis Robinson

Kevin Neal Magill

Michael B Mitchell

Michael P Wilson

Jason Lawrence Panavich

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.

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

Maintaining domain coherence states including Domain State No-Owned (DSN) in processor-based devices is disclosed. In this regard, a processor-based device provides multiple processing elements (PEs) organized into multiple domains, each containing one or more PEs and a local ordering point circuit (LOP). The processor-based device supports domain coherence states for coherence granules cached by the PEs within a given domain. The domain coherence states include a DSN domain coherence state, which indicates that a coherence granule is not cached within a shared modified state within any domain. In some embodiments, upon receiving a request for a read access to a coherence granule, a system ordering point circuit (SOP) determines that the coherence granule is cached in the DSN domain coherence state within a domain of the plurality of domains, and can safely read the coherence granule from the system memory to satisfy the read access if necessary.

Maintaining domain coherence states including domain state no-owned (DSN) in processor-based devices

Providing dynamic selection of cache coherence protocols in processor-based devices is disclosed. In this regard, a processor-based device includes a master PE and at least one snooper PE, as well as a central ordering point (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 by the master PE. The selection is made by the COP based on one or more protocol preference indicators that may be generated and provided by one or more of the master PE, the at least one snooper PE, and the COP itself. After selecting the cache coherence protocol to use, the COP sends a response message to each of the master PE and the at least one snooper PE indicating the selected cache coherence protocol.

Providing dynamic selection of cache coherence protocols in processor-based devices

Enabling atomic memory accesses across coherence granule boundaries in processor-based devices is disclosed. In this regard, a processor-based device includes multiple processing elements (PEs), and further includes a special-purpose central ordering point (SPCOP) configured to distribute coherence granule ('cogran') pair atomic access (CPAA) tokens. To perform an atomic memory access on a pair of coherence granules, a PE must hold a CPAA token for an address block containing one of the pair of coherence granules before the PE can obtain each of the pair of coherence granules in an exclusive state. Because a CPAA token must be acquired before obtaining exclusive access to at least one of the pair of coherence granules, and because the SPCOP is configured to allow only one CPAA token to be active for a given address block, deadlocks and livelocks between PEs seeking to access the same coherence granules can be avoided.

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Raleigh, NC, United States of America

Derek Bachand