Vincent: Green hot methods in the JVM

In this paper, we show the energy efficiency of Java applications can be improved by applying Dynamic Voltage and Frequency Scaling (DVFS) inside the Java Virtual Machine (JVM). We augment the JVM to record the energy consumption of hot methods as the underlying CPU is run at different clock frequencies; after all the frequency possibilities for a method have been explored, the execution of the method in an optimized run is set to the CPU frequency that leads to the most energy-efficient execution for that method. We introduce a new sampling methodology to overcome the dual challenges in our design: both the underlying measurement mechanism for energy profiling and the DVFS for energy optimization are overhead-prone. We extend JikesRVM with our approach and benchmark it over the DaCapo suite on a server-class Linux machine. Experiments show we are able to use 14.9% less energy than built-in power management in Linux, and improve energy efficiency by 21.1% w.r.t. the metric of Energy-Delay Product (EDP).