RAPID: reconfigurable and scalable all-photonic interconnect for distributed shared memory multiprocessors

In this paper, we describe the design and analysis of a scalable architecture suitable for large-scale distributed shared memory (DSM) systems. The approach is based on an interconnect technology which combines optical components and a novel architecture design. In DSM systems, numerous shared memory transactions such as requests, responses and acknowledgment messages propagate simultaneously in the network. As the network size increases, network contention results in increasing the critical remote memory access latency, which significantly penalizes the performance of DSM systems. In our proposed architecture called reconfigurable and scalable all-photonic interconnect for distributed-shared memory (RAPID), we provide high connectivity by maximizing the channel availability for remote communication to reduce the critical remote latency. RAPID provides fast and efficient unicast, multicast and broadcast capabilities using a combination of aggressively designed wavelength division multiplexing (WDM), time division multiplexing (TDM), and space division multiplexing (SDM) techniques. RAPID is wavelength-routed, permitting the same limited set of wavelength to be reused among all processors. We evaluated RAPID based on network characteristics, power budget criteria, and by simulation using synthetic traffic workloads and compared it against other networks such as electrical ring, torus, mesh, and hypercube networks. We found that RAPID outperforms all networks and still provides good performance as the network is scaled to very large numbers.