An Effective Queuing Scheme to Provide Slim Fly Topologies with HoL Blocking Reduction and Deadlock Freedom for Minimal-Path Routing

Interconnection network performance becomes a key issue in HPC systems as their size grows. In order to maximize network performance with the minimum quantity of network resources, Slim Fly topology was proposed. It offers a high network bandwidth and assures a network diameter of two. However, in congestion situations where the head-of-line blocking effect arises, the Slim Fly performance may drop dramatically. To alleviate this problem, we present first in this paper an analysis of congestion dynamics in Slim Fly networks. Then, based on this analysis, we propose the technique Slim Fly 2-Level Queuing (SF2LQ), especially designed for Slim Fly topologies using minimal-path routing. SF2LQ configures several virtual channels (VCs) grouped into two virtual networks to reduce HoL blocking while providing deadlock-free routing. This technique leverages the resources in network devices by efficiently using the available VCs. Finally, through simulation experiments, we show how our proposal boosts network performance while requiring a smaller number of VCs at input port buffers compared to with other techniques.