Restructuring AMS to reduce synchronization overheads on android system

In this paper, we present an optimization method which can be used to improve the performance of android system by reducing the synchronization overheads in the activity manager service (AMS) component. The optimization decreases the waiting time of synchronizations by dividing the original single object lock in AMS into different ones. We use an alias analysis method, i.e. escape analysis, to divide all the synchronized code blocks into different equivalence classes so that there is no intersection of objects accessed for two blocks from different equivalence classes. Then, we can use different object locks to guard these code blocks. We implemented our optimization on android 6.0, and decreased the waiting time of synchronization locks in AMS by 30.9 and 27.7% when the system starts up and runs normally. We find that the distribution of the waiting time for the synchronized lock is in accordance with the characteristics of power-law distribution.