Dynamic Voltage and Frequency Scaling: characterization and usage in the real- world

Benoit PRADELLE
UNIVERSITE DE VERSAILLES SAINT-QUENTIN-EN-YVELINES

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Abstract : Energy consumption recently raised several ecological, technical, and economical concerns. It is now considered as one of the major issues computer science has to face. Several solutions are considered to reduce energy consumption of computers and, among them, Dynamic Voltage and Frequency Scaling (DVFS) emerged as an effective way to enhance power efficiency by adapting processor frequency to workloads.

Even if DVFS is a well-established technology, it is often feared because of its unpredictable effects on performance and energy consumption. On the other hand, many DVFS controllers are not real-world proof because they often ignore recent technology transitions such as multicore processors. We alleviate these issues in two different projects: UtoPeak and FoREST.

UtoPeak is able to determine the maximal amount of energy that can be saved thanks to DVFS for a given program and computer. This energy saving potential can be used to compare different computers or to estimate the efficiency of a particular DVFS controller.

FoREST performs efficient runtime DVFS control on modern processors. It can achieve significant energy savings compared to existing DVFS controllers, under a user-defined performance constraint. While UtoPeak can predict the energy saving potential for a program, FoREST performs efficicent DVFS control while taking great care of the program performance. It is then possible to determine the effects of DVFS on a program and efficiently exploit it on production-grade systems.