Android activity based intelligent hotplug control

Abstract

In multi-core mobile chipsets, when CPU cores are handled through software mechanisms instead of hardware clock gating and power gating, the leakage current i.e. when the cores are active but in idle state, is greater than average expected leakage current. Apart from resulting in power loss, there is a penalty in terms of performance, especially when a user unlocks the device and tries to scroll across the screen, launch an app or rotate the screen. The sudden increase in load leads to sluggish behavior of the device. In this paper, a mechanism is proposed to intelligently enable and disable CPU hotplug based on activities to balance the power and performance of the device. In this solution, the CPU hotplug is disabled for a certain time out period and all the cores are made active so that when the user performs an activity, the sudden load is managed properly. Once the timeout period is over, CPU hotplug is enabled and the cores are then controlled by the governor. The results of this experiment show a significant reduction in leakage power and also results in better performance of the device.