System Noise Revisited: Enabling Application Scalability and Reproducibility with SMT

Despite significant advances in reducing system noise, the scalability and performance of scientific applications running on production commodity clusters today continue to suffer from the effects of noise. Unlike custom and expensive leadership systems, the Linux ecosystem provides a rich set of services that application developers utilize to increase productivity and to ease porting. The cost is the overhead that these services impose on a running application, negatively impacting its scalability and performance reproducibility. In this work, we propose and evaluate a simple yet effective way to isolate an application from system processes by leveraging Simultaneous Multi-Threading (SMT), a pervasive architectural feature on current systems. Our method requires no changes to the operating system or to the application. We quantify its effectiveness on a diverse set of scientific applications of interest to the U. S. Department of Energy showing performance improvements of up to 2.4 times at 16,384 tasks for a high-order finite elements shock hydrodynamics application. Finally, we provide guidance to system and application developers on how to best leverage SMT under different application characteristics and scales.