duf: Dynamic uncore frequency scaling to reduce power consumption

Reducing the power consumption of applications has become one of the key challenges in high-performance computing. Recent processor architectures differentiate processor core frequency from its uncore frequency. As a consequence, in addition to tuning processor core frequency with dynamic voltage and frequency scaling, power consumption can also be controlled through uncore frequency scaling. This article studies how the uncore frequency can be used as a leverage to improve power consumption. We propose duf, a daemon process that dynamically adapts the uncore frequency to reduce an application power consumption with a user-defined limit on performance degradation. The evaluation of duf on three different architectures shows that with no performance degradation (<0.6%), duf can reduce socket power consumption by 7.94%. We also show that duf is able to reduce the total energy consumption by up to 18.20%.