Enabling accurate power profiling of HPC applications on exascale systems

Despite being one of the most important limiting factors on the road to exascale computing, power is not yet considered a "first-class citizen" among the system resources. As a result, there is no clear OS interface that exposes accurate resource power consumption to user-level runtimes that implement power-aware software algorithms. In this work we propose a System Monitor Interface (SMI) between the OS and the user runtime that exposes accurate, per-core power consumption. To make up for the lack of reliable per-core power sensors, we implement a proxy power sensor, based on a regression analysis of core activity, that provides per-core information. SMI effectively hides the implementation details from the user, who has the perception of reading power information from a real sensor. This allows us these proxy sensors to be replaced with real hardware sensors when the latter becomes available, without the need to modify user-level software. Using SMI and the proxy power sensors, we implement a power profiling runtime library and analyzed applications from the NPB benchmark suite and the Exascale Co-Design Centers. Our results show that accurate, per-core power information is necessary for the development of exascale system software and for comprehensively understanding the power characteristics of parallel scientific applications.