Analysis of the Nectar Communication Processor

Nectar is a multicomputer built around a high-bandwidth crosspoint network. Nodes are connected to Nectar using network coprocessors (CABs) that do the protocol processing. The communication coprocessor is based on a general-purpose processor and runs a flexible runtime system. This allows us to offload application on the coprocessor and to experiment with different protocol implementations. An important network parameter for applications is the latency for short messages. In this paper we present an analysis of the CAB-CAB and host-host communication latency over Nectar for a number of communication protocols. We break up the latency and discuss how the components an influenced by the protocol implementation and node architecture.