Path2SL: Optimizing Head-of-Line Blocking Reduction in InfiniBand-Based Fat-Tree Networks

The interconnection network is a key element in high-performance computing (HPC) and Datacenter (DC) systems, as it must support the communication among the endnodes, whose number constantly increases. Hence, guaranteeing a suitable network performance is crucial, as otherwise the network would become the entire system bottleneck. Network performance depends on several design issues: topology and routing, switch architecture, interconnect technology, etc. Among the available interconnect technologies, InfiniBand is a prominent one. InfiniBand components and control software allow to implement efficient topologies and routing algorithms, as well as queuing schemes that reduce the Head-of-Line (HoL) blocking effect derived from congestion situations. In this paper we present a new queuing scheme called Path2SL, that optimizes the use of the InfiniBand Virtual Lanes (VLs) to reduce HoL blocking in Fat-Tree network topologies. We have implemented PathSL in the control software of a real InfiniBand-based cluster. The experiment results obtained from real workloads run in this cluster show that Path2SL is a more efficient queuing scheme than others previously proposed to deal with HoL blocking in the analysed network configurations.