A new proposal to deal with congestion in InfiniBand-based fat-trees

• Cost-efficient network-interconnect designs are a critical task for the HPC Systems.
• Congestion degrades the network performance: congestion management (CM) is required.
• InfiniBand(IB)-based interconnection networks have a strong presence in the HPC Systems.
• Flow2SL is a new CM technique for IB Fat-trees, based on mapping traffic-flows to SLs.
• Flow2SL achieves up to a 68% of improvement compared to the ideal performance gain.

The overall performance of High-Performance Computing applications may depend largely on the performance achieved by the network interconnecting the end-nodes; thus high-speed interconnect technologies like InfiniBand are used to provide high throughput and low latency. Nevertheless, network performance may be degraded due to congestion; thus using techniques to deal with the problems derived from congestion has become practically mandatory. In this paper we propose a straightforward congestion-management method suitable for fat-tree topologies built from InfiniBand components. Our proposal is based on a traffic-flow-to-service-level mapping that prevents, as much as possible with the resources available in current InfiniBand components (basically Virtual Lanes), the negative impact of the two most common problems derived from congestion: head-of-line blocking and buffer-hogging. We also provide a mathematical approach to analyze the efficiency of our proposal and several ones, by means of a set of analytical metrics. In certain traffic scenarios, we observe up to a 68% of the ideal performance gain that could be achieved in HoL-blocking and buffer-hogging prevention.