A novel multicast scheme to reduce cache invalidation overheads in DSM systems

Directory-based write-invalidate cache coherence protocols have been widely used in distributed shared memory (DSM) systems, in which cache invalidation overheads occupy a large part of the system overheads. In this paper, we propose a novel tree-based multidestination multicast scheme TBM which involves a new efficient multidestination message format. TBM combines the best features of two existing approaches: tree-based multicast and multidestination message passing. With the new scheme, only one invalidation message and less than 2/sup [log2(n+1)]-1/ acknowledgement messages are required in one cache invalidation transaction when n processor nodes have the copies of the cache block. Detailed analysis and simulation in 2D mesh show that TBM is preferable to traditional Umesh, Hamiltonian Path and BRCP-HL multicast schemes, which indicates that current and future DSM systems can take advantage of this scheme to deliver better performance.