Improving dynamic voltage scaling algorithms with PACE
Proceedings of the 2001 ACM SIGMETRICS international conference on Measurement and modeling of computer systems
PACE: A New Approach to Dynamic Voltage Scaling
IEEE Transactions on Computers
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This paper addresses algorithms for dynamically scaling CPU speed and voltage in order to save energy. Such scaling is useful and effective when the user will perceive the same performance no matter how long the current task takes, as long as it completes by some deadline. We show that it is possible to modify any scaling algorithm so that performance remains the same but energy consumption may decrease. We then present a formula for modifying an algorithm in this way to minimize expected energy consumption. This formula increases speed as the task progresses, and therefore we call this approach PACE (Processor Acceleration to Conserve Energy). This optimal formula depends on the probability distribution of the task''s work requirement and requires that the speed be varied continuously. We therefore present methods for estimating the task work distribution and evaluate how effective they are on a variety of real workloads. We also show how to approximate the optimal continuous schedule with one that changes speed a limited number of times. Using these methods, we find we can apply PACE practically and efficiently. Furthermore, PACE is extremely effective: simulations using real workloads show that PACE can reduce the CPU energy consumption of classic algorithms by up to 49.5%, with an average of 20.6%, without any effect on performance.