Runtime DVFS control with instrumented Code in power-scalable cluster system

Recently, several energy reduction techniques using DVFS have been presented for PC clusters. This work proposes a Code-instrumented Runtime DVFS control, in which the combination of frequency and voltage (called a gear) is managed at the instrumented code at runtime. The codes are inserted by defining the program regions that have the same characteristics. The Code-instrumented Runtime DVFS control method is better than the Interrupt-based Runtime DVFS control method, in which the gear is managed by periodic interrupt, because it can reflect the program information to control DVFS. Though Static DVFS control, which makes use of the power profile before execution, gives better energy reduction, the proposed Code-instrumented Runtime DVFS control is easier to use, because it requires no information such as profile. The proposed DVFS control method was designed and implemented. The beta-adaptation was used as the runtime algorithm to choose the appropriate gear. The results show that the proposed method can improve the performance and energy consumption compared with Interrupt-based Runtime DVFS control. Although our Code-instrumented Runtime DVFS control can select lower voltages and frequencies than the present Runtime DVFS control given a certain deadline, unfortunately, it was also found to increase power consumption of the PC cluster due to an increase in the execution time.