USENIX Association Proceedings of MobiSys 2003: The First International Conference on Mobile Systems, Applications, and Services San Francisco, CA, USA May 5-8, 2003 © 2003 by The USENIX Association All Rights Reserved For more information about the USENIX Association: Phone: 1 510 528 8649 FAX: 1 510 548 5738 Email:
[email protected] WWW: http://www.usenix.org Rights to individual papers remain with the author or the author's employer. Permission is granted for noncommercial reproduction of the work for educational or research purposes. This copyright notice must be included in the reproduced paper. USENIX acknowledges all trademarks herein. Operating System Modifications for Task-Based Speed and Voltage Scheduling Jacob R. Lorch Alan Jay Smith Microsoft Research University of California, Berkeley 1 Microsoft Way EECS Department, Computer Science Division Redmond, WA 98052 Berkeley, CA 94720-1776
[email protected] [email protected] Abstract lower voltages mean lower energy consumption. Lower voltages, however, necessitate lower CPU speeds, pre- This paper describes RightSpeed, a task-based speed senting an interesting operating system issue: how to en- and voltage scheduler for Windows 2000. It takes ad- sure that performance remains reasonable while some- vantage of the ability of certain processors, such as those times lowering speed to save energy. from Transmeta and AMD, to dynamically change speed Traditionally, systems use interval-based strategies. and voltage and thus to save energy while running more Such strategies divide time into intervals of fixed length slowly. RightSpeed uses PACE, an algorithm that com- and set the speed for each interval based on recent CPU putes the most energy efficient way to meet task dead- utilization.