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

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activity levels to 30%. Since processors have a finite number of architected DVFS states,<br />

the algorithm selects the nearest frequency which meets the target activity level.<br />

Core Activity Level<br />

100%<br />

90%<br />

80%<br />

70%<br />

60%<br />

50%<br />

40%<br />

30%<br />

20%<br />

10%<br />

0%<br />

=<br />

Increase<br />

Frequency<br />

Increase Threshold = 50%<br />

No Change<br />

Decrease Threshold = 30%<br />

Decrease<br />

Frequency<br />

126<br />

<br />

+ <br />

Figure 7.2: Windows Vista Reactive P-State Selection Algorithm<br />

7.3 Workload Characterization<br />

High Per<strong>for</strong>mance<br />

Demand<br />

Region<br />

Hysteresis<br />

Region<br />

Low Per<strong>for</strong>mance<br />

Demand<br />

Region<br />

To analyze the power/per<strong>for</strong>mance impact of the predictive power management scheme<br />

on real-world workloads, a system running the desktop/client SYSmark 2007 benchmark<br />

is characterized. This benchmark represents a wide range of desktop computing<br />

applications. <strong>The</strong> benchmark components are E-Learning, Video Creation, Productivity,<br />

and 3D. <strong>The</strong> individual subtests are listed in Table 7.1. This benchmark is particularly<br />

important to the study of dynamic power adaptations since it provides realistic user<br />

scenarios that include user interface and I/O delays. <strong>The</strong>se delays cause a large amount

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