A Lightweight Pseudo CPU Hotplug Mechanism for Mobile Devices

Power efficiency has become one of the most important issues in mobile devices because of their limited battery size. However, many mobile applications and processors negatively accelerate power consumption of mobile devices. Previous work (e.g., CPU hotplug) may be inappropriate in mobile devices due to their slow responsiveness because it has to migrate all processes running on a CPU, which is to be turned off to save power consumption, to another CPU, thereby resulting in slow responsiveness. In this paper, we propose a novel mechanism, called pseudo CPU hotplug, which efficiently guarantees fast responsiveness while reducing the power consumption of mobile devices. Our mechanism eliminates almost all overhead of operation system such as that of synchronous task migration, and leaves only architecture-dependent overhead of entering deep idle mode. Our evaluation results clearly show that pseudo CPU hotplug outperforms the traditional CPU hotplug mechanism by up to 997 times in terms of response latency. In addition, our mechanism increases the time spent in deep idle mode more than 30% compared to normal status.