Integrating Real Time and Power Management in a Real System

Deploying dynamic voltage and frequency scaling (DVFS) techniques in a real-time context has generated some interest in recent years. However, most of this work is based on highly simplifying assumptions regarding the cost and benefit of frequency scaling. We have integrated a measurement-based DVFS technique with an EDF based scheduling framework. This enables the use of the dynamic slack caused by the variability of execution time, to reduce energy consumption and thus extend battery life or reduce thermal load. We have tested the approach using hardware instrumentation on a real system. This paper describes not only the theoretical basis for the work, but also our experiences with DVFS when confronted with physical reality.