Reactive DVFS Control for Multicore Processors.

Several solutions are considered to reduce energy consumption of computers. Among them, Dynamic Voltage and Frequency Scaling (DVFS) emerged as an effective way to enhance energy efficiency by adapting processor frequency to workloads. We propose Forest, a new DVFS controller designed to efficiently exploit the recent technologies introduced in processors. Forest is a runtime DVFS controller able to estimate the energy savings it can achieve from power gains, evaluated offline using power probes embedded in modern CPUs, and speedups measured at runtime for the current workload. It does not use any performance model but rather directly measures the effect of frequency transitions on energy. Using such methodology, Forest can achieve energy savings on the whole system under user-defined slowdown constraints. In our experiments, Forest is able to achieve more than 39% CPU energy savings compared to the default Linux DVFS controller, with a slowdown below 5%, as requested by the user.