Efficient virtual interface architecture (VIA) support for the IBM SP switch-connected NT clusters

The IBM SP Switch-Connected NT cluster is one the newest clustering platforms available. In this paper, we discuss an experimental implementation of the Virtual Interface Architecture for this platform. We discuss different design issues involved in this implementation. In particular, we explain how the virtual-to-physical address translation can be implemented efficiently with a minimum Network Interface Card (NIC) memory requirement. We show how caching the VIA descriptors on the NIC can reduce the communication latency. We also present an efficient scheme for implementing the VIA door bells without any hardware support. A comprehensive performance evaluation study of the implementation is provided. The performance of the implemented VIA surpasses that of other existing software implementations of the VIA and is comparable to that of a hardware VIA implementation. The peak measured bandwidth for our system is observed to be 101.4 MBytes/s and the one-way latency for short messages is 18.2 microseconds. It is to be noted that the VIA implementation presented in this paper is not a part of any IBM product and no assumptions should be made regarding its availability as a product in the future