(SAI) Stalled, Active and Idle: Characterizing Power and Performance of Large-Scale Dragonfly Networks

Exascale networks are expected to comprise a significant part of the total monetary cost and 10-20% of the power budget allocated to exascale systems. Yet, our understanding of current and emerging workloads on these networks is limited. Left ignored, this knowledge gap likely will translate into missed opportunities for (1) improved application performance and (2) decreased power and monetary costs in next generation systems. This work targets a detailed understanding and analysis of the performance and utilization of the dragonfly network topology. Using the Structural Simulation Toolkit (SST) and a range of relevant workloads on a dragonfly topology of 110,592 nodes, we examine network design tradeoffs amongst execution time, power, bandwidth, and the number of global links. Our simulations report stalled, active and idle time on a per-port level of the fabric, in order to provide a detailed picture of future networks. The results of this work show potential savings of 3-10% of the exascale power budget and provide valuableinsights to researchers looking for new opportunities to improve performance and increase power efficiency of next generation HPC systems.