Copyright by William Lloyd Bircher 2010 - The Laboratory for ...

adaptations. In contrast, the disk subsystem has 18.5% of samples definable as 100 ms
phases, thus providing greater opportunity to amortize adaptation costs. While chipset
and memory subsystems have a large percentage of classifiable samples, they may not be
viable candidates for adaptation. By also considering that most of the chipset and
memory samples are close to the average, standard deviations of 0.9 Watts and 1.4 Watts
respectively, there may be insufficient variation for runtime phase detection.
Table 4.3 Percent of Classifiable Samples
Duration (ms) CPU Chipset Memory I/O Disk
CoV = 0.25
1 98.5 100 100 99.5 100
10 90.8 100 100 87.6 100
100 70.0 100 100 85.3 100
1000 36.0 100 100 96.3 100
Error % 8.78 3.70 3.47 15.2 6.31
CoV = 0.10
1 91.7 100 100 81.1 100
10 66.0 100 98.6 35.7 88.6
100 43.1 100 94.4 21.0 95.6
1000 9.30 100 93.1 0.00 95.0
Error % 4.60 3.70 3.47 6.63 6.31
CoV = 0.05
1 61.6 88.3 97.7 22.4 98.4
10 25.5 78.0 91.2 1.70 32.1
100 6.00 63.2 78.6 0.00 18.5
1000 0.00 64.4 50.0 0.00 0.00
Error % 3.38 3.46 2.68 3.67 2.93
From these results, it is clear that distinct phases are detectable at granularities ranging
from seconds to milliseconds. The next step in utilizing the phases is to combine the
amplitude and duration results to direct power management strategies. An example
classification is given in Table 4.4.
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