DEP+BURST: Online DVFS Performance Prediction for Energy-Efficient Managed Language Execution

Making modern computer systems energy-efficient is of paramount importance. Dynamic Voltage and Frequency Scaling (DVFS) is widely used to manage the energy and power consumption in modern processors; however, for DVFS to be effective, we need the ability to accurately predict the performance impact of scaling a processor's voltage and frequency. No accurate performance predictors exist for multithreaded applications, let alone managed language applications. In this work, we propose DEP+BURST, a new performance predictor for managed multithreaded applications that takes into account synchronization, interthread dependencies, and store bursts, which frequently occur in managed language workloads. Our predictor lowers the performance estimation error from 27 percent for a state-of-the-art predictor to 6 percent on average, for a set of multithreaded Java applications when the frequency is scaled from 1 to 4 GHz. We also novelly propose an energy management framework that uses DEP+BURST to reduce energy consumption. We first target reducing the processor's energy consumption by lowering its frequency and hence its power consumption, while staying within a user-specified maximum slowdown threshold. For a slowdown of 5 and 10 percent, our energy manager reduces on average 13 and 19 percent of energy consumed by the memory-intensive benchmarks. We then use the energy manager to optimize total system energy, achieving an average reduction of 15.6 percent for a set of Java benchmarks. Accurate performance predictors are key to achieving high performance while keeping energy consumption low for managed language applications using DVFS.