Reducing Static Energy in Supercomputer Interconnection Networks Using Topology-Aware Partitioning

Abstract

The key to reducing static energy in supercomputers is switching off their unused components. Routers are the major components of a supercomputer. Whether routers can be effectively switched off or not has become the key to static energy management for supercomputers. For many typical applications, the routers in a supercomputer exhibit low utilization. However, there is no effective method to switch the routers off when they are idle. By analyzing the router occupancy in time and space, for the first time, we present a routing-policy guided topology partitioning methodology to solve this problem. We propose topology partitioning methods for three kinds of commonly used topologies (mesh, torus and fat-tree) equipped with the three most popular routing policies (deterministic routing, directionally adaptive routing and fully adaptive routing). Based on the above methods, we propose the key techniques required in this topology partitioning based static energy management in supercomputer interconnection networks to switch off unused routers in both time and space dimensions. Three topology-aware resource allocation algorithms have been developed to handle effectively different job-mixes running on a supercomputer. We validate the effectiveness of our methodology by using Tianhe-2 and a simulator for the aforementioned topologies and routing policies. The energy savings achieved on a subsystem of Tianhe-2 range from 3.8 to 79.7 percent. This translates into a yearly energy cost reduction of up to half a million US dollars for Tianhe-2.