Inter-node networks are a key capability of High-Performance Computing (HPC) systems that differentiates them from less capable classes of machines. However, in spite of their very high performance, the increasing computational power of HPC compute nodes and the associated rise in application communication needs make network performance a common performance bottleneck. To achieve high performance in spite of network limitations application developers require tools to measure their applications’ network utilization and inform them about how the network’s communication capacity relates to the performance of their applications. This paper presents a new performance measurement and analysis methodology based on empirical measurements of network behavior. Our approach uses two benchmarks that inject extra network communication. The first probes the fraction of the network that is utilized by a software component (an application or an individual task) to determine the existence and severity of network contention. The second aggressively injects network traffic while a software component runs to evaluate its performance on less capable networks or when it shares the network with other software components. We then combine the information from the two types of experiments to predict the performance slowdown experienced by multiple software components (e.g. multiple processes of a single MPI application) when they share a single network. Our methodology is applied to individual network switches and demonstrated taking 6 representative HPC applications and predicting the performance slowdowns of the 36 possible application pairs. The average error of our predictions is less than 10%.

The research leading to these results has received funding from the European Research Council under the European Union’s 7th FP (FP/2007-2013) / ERC GA n. 321253. Work partially supported by the Spanish Ministry of Science and Innovation (TIN2012-34557). This article has been authored in part by Lawrence Livermore National Security, LLC under Contract DE-AC52-07NA27344 with the U.S. Department of Energy. Accordingly, the United States Government retains and the publisher, by accepting the article for publication, acknowledges that the United States Government retains a non-exclusive, paid-up, irrevocable, world-wide license to publish or reproduce the published form of this article or allow others to do so, for United States Government purposes. This work was partially supported by the Department of Energy Office of Science (Advanced Scientific Computing Research) Early Career Grant, award number NA27344.

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