Boosting the performance of Myrinet networks

Networks of workstations (NOWs) are becoming increasingly popular as a cost-effective alternative to parallel computers. These networks allow the customer to connect processors using irregular topologies, providing the wiring flexibility, scalability and incremental expansion capability required in this environment. Some of these networks use source routing and wormhole switching. In particular, we are interested in Myrinet networks because they are a well-known commercial product and their behavior can be controlled by the software running on the network interfaces (the Myrinet Control Program, MCP). Usually, the Myrinet network uses up*/down* routing for computing the paths for every source-destination pair. In this paper, we propose an in-transit buffer (ITB) mechanism to improve the network performance. We apply the ITB mechanism to NOWs with up*/down* source routing, like the Myrinet, analyzing its behavior on networks with both regular and irregular topologies. The proposed scheme can be implemented on Myrinet networks by simply modifying the MCP, without changing the network hardware. We evaluate by simulation several networks with different traffic patterns using timing parameters taken from the Myrinet network. The results show that the current routing schemes used in Myrinet networks can be strongly improved by applying the ITB mechanism. In general, our proposed scheme is able to double the network throughput on medium and large NOWs. Finally, we present a first implementation of the ITB mechanism on a Myrinet network.