User-Centric Power Management for Embedded CPUs Using CPU Bandwidth Control

Dynamic power management for mobile processors has become very important due to the increased clock speed and number of cores. There have been various power management governors using dynamic voltage and frequency scaling (DVFS). Among them, a user-centric power management has received a lot of attention as a method to save power while maintaining the quality of user experience (UX) referring to the perceived quality of system services to end users. Most user-centric governors have employed DVFS as a method to reduce the power consumption. However, DVFS may not be adequate enough to guarantee UX qualities for all task because the CPU clock speed changed by DVFS can affect all tasks running at the same processor. In order to minimize such inter-task interferences by DVFS, it is necessary to employ task-specific power management methods. This paper shows that CPU bandwidth control developed for CPU resource management within Linux kernel can be employed as a task-specific power management method, and a novel CPU power management scheme employing both DVFS and CPU bandwidth control is proposed. Experimental results show that the proposed governor can reduce the power consumption more than the Ondemand governor can achieve while maintaining the quality of UX.