Overlapping Computation and Communication in SMT Clusters with Commodity Interconnects

Abstract—In this paper we focus on optimizing the perfor-mance in a cluster of Simultaneous Multithreading (SMT) processors connected with a commodity interconnect (e.g. Gbit Ethernet), by applying overlapping of computation with communication. As a test case we consider the parallelized advection equation and discuss the steps that need to be followed to semantically allow overlapping to occur. We propose an implementation based on the concept of Helper Threading that distributes computation and communication in the two sibling threads of an SMT processor, thus creating an asym-metric pair of execution patterns in each hardware context. Our experimental results in an 8-node cluster interconnected with commodity Gbit Ethernet demonstrate that the proposed implementation is able to achieve substantial performance improvements that can exceed 20 % in some cases, by efficiently utilizing the available resources of the SMT processors. Keywords-SMT architecture; overlapping; I