Building Efficient Limited Directory-Based DSMs: A Multidestination Message Passing Based

Abstract

: A cost-effective distributed shared memory (DSM) system typically uses a limited directory protocol to enforce cache coherence. This paper presents a new family of protocols, called Limited directory with Region-based Broadcast (Limited-RB), to efficiently implement cache coherence in wormhole routed DSM systems. This protocol family uses multidestinationbased cache invalidation mechanisms to distribute invalidation requests to and collect the associated acknowledgments from separate regions. As a result, a write invalidation can be accomplished with fewer messages, less network traffic, and reduced occupancy at home nodes. These reductions contribute to decreasing invalidation latency and improving overall system performance. Directory organization under this new protocol is developed for 2D systems with e-cube routing and evaluated through simulations for a set of applications. The results indicate that with a small directory storage, the Limited-RB protocol family can achieve supe..