Ultra-High Performance Communication with MPI and the Sun Fire ™ Link Interconnect

We present a new low-latency system area network that provides the ultra-high bandwidth needed to fuse a collection of large SMP servers into a capability cluster. The network adapter exports a remote shared memory (RSM) model that supports low latency kernel bypass messaging. The Sun™ MPI library uses the RSM interface to implement a highly efficient memory-to-memory messaging protocol in which the library directly manages buffers and data structures in remote memory. This allows flexible allocation of buffer space to active connections, while avoiding resource contention that could otherwise increase latencies. We discuss the characteristics of the interconnect, describe the MPI protocols, and measure the performance of a number of MPI benchmarks. Our results include MPI inter-node bandwidths of almost 3 Gigabytes per second and MPI ping-pong latencies as low as 3.7 microseconds.