OSDI '02 Abstract
Vertigo: Automatic Performance-Setting for Linux
Krisztián Flautner, ARM Limited; Trevor Mudge, University of Michigan
Combining high performance with low power consumption
is becoming one of the primary objectives of
processor designs. Instead of relying just on sleep mode
for conserving power, an increasing number of processors
take advantage of the fact that reducing the clock
frequency and corresponding operating voltage of the
CPU can yield quadratic decrease in energy use. However,
performance reduction can only be beneficial if it
is done transparently, without causing the software to
miss its deadlines. In this paper, we describe the implementation
and performance-setting algorithms used in
Vertigo, our power management extensions for Linux.
Vertigo makes its decisions automatically, without any
application-specific involvement. We describe how a
hierarchy of performance-setting algorithms, each specialized
for different workload characteristics, can be
used for controlling the processor's performance. The
algorithms operate independently from one another
and can be dynamically configured. As a basis for comparison
with conventional algorithms, we contrast
measurements made on a Transmeta Crusoe-based
computer using its built-in LongRun power manager
with Vertigo running on the same system. We show that
unlike conventional interval-based algorithms like LongRun,
Vertigo is successful at focusing in on a small
range of performance levels that are sufficient to meet
an application's deadlines. When playing MPEG movies,
this behavior translates into a 11%-35% reduction
of mean performance level over LongRun, without any
negative impact on the framerate. The performance
reduction can in turn yield significant power savings.
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