Efficient Queuing Schemes for HoL-Blocking Reduction in Dragonfly Topologies with Minimal-Path Routing

HPC systems are growing in number of connected endnodes, making the network a main issue in their design. In order to interconnect large systems, dragonfly topologies have become very popular in the latest years as they achieve high scalability by exploiting high-radix switches. However, dragonfly high performance may drop severely due to the Head-of-Line (HoL) blocking effect derived from congestion situations. Many techniques have been proposed for dealing with this harmful effect, the most effective ones being those especially designed for a specific topology and a specific routing algorithm. In this paper we present a queuing scheme called Hierarchical Two-Levels Queuing, designed speci…