Alleviating the impact of tree saturation on multistage interconnection network performance

Abstract

Tree saturation in a multistage interconnection network due to hotspot access can result in drastically degraded bandwidth and mean latency. Several solutions for preventing tree saturation or avoiding traffic congestion, enhancing overall network band-width and latency, have been proposed. One class of these solutions may be effective in many situations, but tends to offer disappointing performance when hotspot requests are not combinable, whereas the other class of solutions is generally applicable to all situations, but often gives rise to decreased bandwidth under uniform traffic when no hotspot exists. In this paper, we investigate a new approach that can provide good performance regardless of whether hotspot requests are combinable and, in addition, can improve network bandwidth in the absence of a hotspot. This is made possible by utilizing multiqueues at switch inputs and at network primary inputs to ensure a considerably larger traffic flow toward memory modules under both uniform and nonuniform reference patterns. Simulation studies reveal that if hotspots are present, this approach indeed alleviates the impact of tree saturation on regular requests effectively, exhibiting a performance better than that of most prior solutions. With its general applicability and reasonably low hardware complexity, the proposed approach appears to be readily suitable for practical applications.