MobiSys '03 Abstract
Operating System Modifications for Task-Based Speed and Voltage Scheduling
Jacob R. Lorch, Microsoft Research; Alan Jay Smith, University of California, Berkeley
This paper describes RightSpeed, a task-based speed and voltage
scheduler for Windows 2000. It takes advantage of the ability of
certain processors, such as those from Transmeta and AMD, to
dynamically change speed and voltage and thus to save energy while
running more slowly. RightSpeed uses PACE, an algorithm that computes
the most energy efficient way to meet task deadlines with high
probability. Since most applications do not provide enough data about
tasks, such as task deadlines, for PACE to work, RightSpeed uses
simple and efficient heuristics to automatically detect task
characteristics for such applications. RightSpeed has
only 1.2% background overhead and its operations take only a few
microseconds each. It even performs PACE calculation, which is quite
complicated, in only 4.4 µs on average due to our extensive
optimizations. RightSpeed is effective at meeting
performance targets set by applications to within 1.5%.
Although the PACE calculator does not save energy for the current
generation of processors due to their limited range of worthwhile
speed and voltage settings, we expect future processors to have
greater such ranges, enabling PACE to reduce CPU energy consumption by
6.1-8.7% relative to the best standard algorithm. Furthermore,
with PACE, giving a processor the ability to run at additional,
higher speeds and voltages reduces overall energy consumption.
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