power aware 35 - PowerScope: A Tool for Profiling the...

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PowerScope: A Tool for Profiling the Energy Usage of Mobile Applications Jason Flinn and M. Satyanarayanan School of Computer Science Carnegie Mellon University jflinn,satya @cs.cmu.edu Abstract In this paper, we describe the design and implementation of PowerScope, a tool for profiling energy usage by appli- cations. PowerScope maps energy consumption to program structure, in much the same way that CPU profilers map processor cycles to specific processes and procedures. Our approach combines hardware instrumentation to measure current level with kernel software support to perform statis- tical sampling of system activity. Postprocessing software maps the sample data to program structure and produces a profile of energy usage by process and procedure. Using PowerScope, we have been able to reduce the energy con- sumption of an adaptive video playing application by 46%. 1. Introduction Energy is a critical resource for mobile computers [5, 8]. In spite of many improvements in low-power hardware de- sign and battery life, there is now growing awareness that a strategically viable approach to energy management must include higher levels of the system [2]. For example, a net- work application that offers acceptable service while tem- porarily disconnected can save a considerable amount of energy by suppressing non-essential wireless communica- tion. The resulting savings add to those offered by energy- efficient hardware. In contrast, efforts aimed solely at the hardware cannot benefit from application-specific knowl- edge. Progress in energy-efficient software design requires the ability to attribute energy consumption to specific software components, in much the same way that CPU profilers such This research was sponsored by the Defense Advanced Research Projects Agency (DARPA), Air Force Materiel Command, USAF under agreement number F19628- 96-C-0061, the Intel Corporation, and AT&T Corporation. The views and conclu- sions contained herein are those of the authors and should not be interpreted as neces- sarily representing the official policies or endorsements, either expressed or implied, as prof and gprof help expose code components that are wasteful of processor cycles. In this paper, we describe a tool called PowerScope that we have built to profile energy usage. PowerScope maps energy consumption to program structure. Using PowerScope, one can determine what frac- tion of the total energy consumed during a certain time pe- riod is due to specific processes in the system. Further, one can drill down and determine the energy consumption of different procedures within a process. By providing such fine-grained feedback, PowerScope allows attention to be focused on those system components responsible for the bulk of energy consumption. As improvements are made to these components, PowerScope quantifies their benefits and helps expose the next target for optimization. Through suc- cessive refinement, a system can be improved to the point
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power aware 35 - PowerScope: A Tool for Profiling the...

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