Efficient implementation of tree-based multicast routing for distributed shared-memory multiprocessors

This paper presents an efficient routing and flow control mechanism to implement multidestination message passing in wormhole networks. It is targeted to situations where the size of message data is very small, like in invalidation and update messages in distributed shared-memory multiprocessors (DSMs) with hardware cache coherence. The mechanism is a variation of tree-based multicast with pruning to avoid deadlocks. The new scheme does not require that the destination addresses in a given multicast message be ordered, thereby avoiding any ordering overhead. It allows messages to use any deadlock-free routing function and only requires one startup for each multicast message. The new scheme has been evaluated on several k-ary n-cube networks under synthetic loads. The results show that the proposed scheme is faster than other multicast mechanisms when the multicast traffic is composed of short messages.