SynchronizationCoherence:ATransparentHardwareMechanismfor CacheCoherenceandFine-GrainedSynchronization

The quest to improve performance forces designers to explore flner-grained multiprocessor machines. Ever increasing chip densities based on CMOS improvements fuel research in highly parallel chip multiprocessors with 100s of processing elements. With such increasing levels of parallelism, synchronization is set to become a major performance bottleneck and e‐cient support for synchronization an important design criterion. Previous research has shown that integrating support for flne-grained synchronization can have signiflcant performance beneflts compared to traditional coarse-grained synchronization. Not much progress has been made in supporting flne-grained synchronization transparently to processor nodes: a key reason perhaps why wide adoption has not followed. In this paper, we propose a novel approach called Synchronization Coherence that can provide transparent flnegrained synchronization and caching in a multiprocessor machine and single-chip multiprocessor. Our approach merges flne-grained synchronization mechanisms with traditional cache coherence protocols. It reduces network utilization as well as synchronization related processing overheads while adding minimal hardware complexity as compared to cache coherence mechanisms or previously reported flne-grained synchronization techniques. In addition to its beneflt of making synchronization transparent to processor nodes, for the applications studied, it provides up to 23% improvement in performance and up to 24% improvement in energy e‐ciency with no L2 caches compared to previous flne-grained synchronization techniques. The performance improvement increases up to 38% when simulating with an ideal L2 cache system.

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