Dynamic Processor Overclocking for Improving Performance of Power-Constrained Systems

Power and thermal constraints are proving to be limiting factors for computer system performance. Conventional approaches estimate a design power and cooling limit based on consumption for a specific, worst-case workload while operating at a nominal frequency. The system is then constrained to operate at or below this frequency even for workloads that have lower power and cooling requirements. As a consequence real workloads pay a performance cost for operating at a design point defined by the worst-case workloads. In this work, we propose Dynamic Processor Overclocking as a way of reducing the performance impact of the chosen design point for workloads that have sufficient slack in their power and cooling requirements. Dynamic Processor Overclocking utilizes the Dynamic Voltage and Frequency Scaling (DVS) capabilities of processors to obtain increased performance in power-constrained systems. While DVS has been widely studied in recent years, solutions exploiting it have focused on saving energy. In contrast, our proposal incorporates DVS for performance enhancement.

The paper focuses on the evaluation of the effectiveness of Dynamic Processor Overclocking using the SPEC CPU2000 benchmarks as a representative set of programs. We identify the workload characteristics that impact the benefit obtained from overclocking. We also investigate the relationship between the severity of the power constraints and application characteristics that determine the overclocking benefits. Our work presents a new approach to improving performance in power-constrained systems, and the insight and methodology required for analyzing its effectiveness for interesting workloads.