Prioritized physical channel scheduling in wormhole networks

The multiplexing and arbitration of the physical channel among many virtual channels is an important issue in parallel systems using wormhole switching technique. Many existing multicomputer routers do not provide support for prioritized traffic at the link level. The main goal of network designers has been to improve average delay and throughput. In this paper, we propose a new, low-cost prioritized physical channel scheduling scheme for wormhole networks. Conventional demand multiplexing allows a set of ready flits to share a physical channel in a strict round-robin manner. Thus, it does not allow flexibility for fast movement of high priority messages such as synchronization and control information. The proposed scheme allows high priority flits to bypass low priority flits, while applying round-robin among flits with the same priority. This paper presents the motivation behind the proposed scheme, description of the scheme, and its implementation. The prioritized physical channel scheduling scheme is evaluated and compared against the conventional demand multiplexing for a wide range of system parameters. Results based on thorough simulation show that the performance of high priority traffic can be significantly improved, latency can be improved by up to 45%. The results demonstrate significant potential for designing high performance wormhole systems to support prioritized traffic.