GRAP: Group-level Resource Allocation Policy for Reconfigurable Dragonfly Network in HPC

Dragonfly is a highly scalable, low-diameter, and cost-efficient network topology, which has been adopted in new exascale High Performance Computing (HPC) systems. However, Dragonfly topology suffers from the limited direct links between groups. The reconfigurable network can solve this problem by reconfiguring topology to adjust the number of direct links between groups. While the performance improvement of a single job on reconfigurable HPC network has been evaluated in previous works, the performance of HPC workloads has not been studied because of the lack of an appropriate resource allocation policy. In this work, we propose Group-level Resource Allocation Policy (GRAP) to allocate both compute nodes and Reconfigurable Links for jobs in Reconfigurable Dragonfly Network (RDN). We start with formulating three design principles: reconfigurable network should be reconfiguration interference-free, guarantee connectivity and performance for each job, and satisfy varied resource requests. According to the principles, GRAP uses different strategies for small and large jobs, and contains three allocation modes for large jobs: Balance Mode, Custom Mode, and Adaptive Mode. Finally, we evaluate GRAP with the CODES network simulation framework and the Slurm Simulator using real workload traces. The results demonstrate that RDN coupled with GRAP achieves lower latency, higher bandwidth, and lower job wait time.