Dynamic voltage and frequency scaling (DVFS) is a key technique for reducing processor power consumption in mobile devices. In recent years, mobile system-on-chips (SoCs) has supported DVFS for embedded graphics processing units (GPUs) as the processing power of embedded GPUs has been increasing steadlily. The major challenge of applying DVFS to a processing unit is to meet the quality of service (QoS) requirement while achieving a reasonable power reduction. In the case of GPUs, the QoS requirement can be specified as the frame-per-second (FPS) which the target GPU should achieve. The proposed DVFS technique ensures a consistent GPU performance by scaling the operating clock frequency in a way that it maintains a uniform FPS.

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Dynamic power management (DPM), which exploits low-power states of the target device, has been a key research issue to overcome the limited battery life of mobile devices. For efficient power management, today's power management unit in a system-on-chip for mobile devices supports multiple low-power states for embedded processors. Unfortunately, the DPM policies implemented in modern operating systems are not appropriate for processors because they may not understand the idleness of the processor accurately. There may be significant performance degradation if the DPM policy module misunderstands that the processor is idle even when there are many interrupt requests to handle. A novel DPM scheme for embedded processors considering the system response time as well as power reduction is proposed. Experimental results show that the proposed DPM policy achieves performance improvement by up to 25% compared to a conventional DPM policy with a similar amount of power reduction.

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