Date: 17 Nov 2006

Network interface active messages for low overhead communication on SMP PC clusters

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NICAM is a communication layer for SMP PC clusters connected via Myrinet, designed to reduce overhead and latency by directly utilizing a micro-processor equipped on the network interface. It adopts remote memory operations to reduce much of the overhead found in message passing. NICAM employs an Active Messages framework for flexibility in programming on the network interface, and this flexibility will compensate for the large latency resulting from the relatively slow micro-processor. Running message handlers directly on the network interface reduces the overhead by freeing the main processors from the work of polling incoming messages. The handlers also make synchronizations faster by avoiding the costly interactions between the main processors and the network interface. In addition, this implementation can completely hide latency of barriers in data-parallel programs, because handlers running in the background of the main processors allow reposition of barriers to any place where the latency is not critical.