Mitigating Interactive Performance Degradation From Mobile Device Thermal Throttling

Abstract

Mobile devices are limited in mass and volume, reducing the viability of active device cooling implementations. This requires the use of less effective passive techniques to maintain device skin temperature levels. Application performance demands on a modern mobile device are driven by sustained performance workloads, such as 3-D games, virtual, and augmented reality. Mobile system-on-chips (SoCs) have corresponding increases in performance through both architectural changes and frequency of operation increases, which has resulted in the peak power consumption exceeding the sustainable thermal envelope defined by device skin temperature requirements. Existing thermal throttling techniques mitigate this by capping the frequency of operation of the SoC. Through experimentation with a modern smartphone platform using sequences from real-world applications, we demonstrate in this letter that frequency capping (FC) can have a significant effect on the performance of interactive applications, increasing the number of frame rate defects by up to 146%. We propose task utilization scaling, a new lever for thermal throttling, which scales performance for critical interactive periods by the same factor as noncritical periods. Experiments demonstrate that the proposed approach can result in a decrease in frame rate defects of up to 18% compared with FC or a skin temperature reduction of up to 2°C.