Modeling CPU Energy Consumption of HPC Applications on the IBM POWER7

Energy consumption optimization of HPC applications inherently requires measurements for reference and comparison. However, most of today´s systems lack the necessary hardware support for power or energy measurements. Furthermore, in-band data availability is preferred for specific optimization techniques such as auto-tuning. For this reason, we present in-band energy consumption models for the IBM POWER7 processor based on hardware counters. We demonstrate that linear regression is a suitable means for modeling energy consumption, and we rely on already available, high-level benchmarks for training instead of self-written or hand-tuned micro-kernels. We compare modeling efforts for different instruction mixes caused by two compilers (GCC and IBM XL) as well as various multi-threading usage scenarios, and validate across our training benchmarks and two real-world applications. Results show mean errors of approximately 1% and overall max errors of 5.3% for GCC.