In this paper, we demonstrate that a collaborative relationship between the operating system and applications can be used to meet user-specified goals for battery duration. We first show how applications can dynamically modify their behavior to conserve energy. We then show how the Linux operating system can guide such adaptation to yield a batterylife of desired duration. By monitoring energy supply and demand, it is able to select the correct tradeoff between energy conservation and

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... n quality. Our evaluation shows that this approach can meet goals that extend battery life by as much as 30%. Profiling Computer ML~meter DOtQ Collection Computer PC / PID C_,~reloted Somples Current Levels This hardware setup is used during PowerScope data collection. A data collection computer distinct from the profiling computer controls the multimeter and stores samples from it. Later, program counter and process id samples are correlated offline with current levels to yield energy profiles.