Reducing coherence overhead in shared-bus multiprocessors

To reduce the overhead of cache coherence enforcement in shared-bus multiprocessors, we propose a self-invalidation technique as an extension to write-invalidate protocols. The technique speculatively identifies cache blocks to be invalidated and dynamically determines when to invalidate them locally. We also consider enhancing our selfinvalidation scheme by incorporating read snarfing, to reduce the cache misses due to incorrect prediction. We evaluate our self-invalidation scheme by simulating SPLASH-2 benchmark programs that exhibit various reference patterns, under a realistic shared-bus multiprocessor model. We discuss the effectiveness and hardware complexity of self-invalidation and its enhancement with read snarfing in our extended protocol.