Execution Based Evaluation of MINs for Cache-Coherent Multiprocessors

In this paper, performance of multistage interconnection networks with wormhole routing and packet switching has been evaluated for cache-coherent shared-memory multiprocessors. The evaluation is based on execution-driven simulation using various applications. The traffic in cache-coherent systems is very different from the traffic in message-passing environments and is characterized by traffic bursts, one-to-many and many-to-one traffic, and small fixed length messages. The performance of packet switching and wormhole routing has been evaluated for different buffer sizes. The comparison of execution time between packet-switched and wormhole-routed networks for the same amount of buffer space per switch shows that wormhole-routed networks provide significant advantages over packet-switched networks. We have also evaluated wormhole networks with virtual channels for variable numbers of virtual channels and flit buffers per channel. The study show s that for wormhole routing, four virtual channels per link and four flit buffers per channel is the best configuration in most of the cases.