The CPU is one of the most battery-consuming elements in a smartphone. The power consumption and user experience are in a trade-off relationship. These can be controlled by the CPU clock rate. Increasing the clock rate makes the user experience better and power consumption worse. On the contrary, the user experience declined and power consumption savings is improved by decreasing the rate. Thus, the clock rate should be increased only when large CPU resources are required. In our previous work, we proposed a concept of increasing the clock rate at an invocation of a CPU-consuming and time-consuming method. However, we did not discuss whether there are method invocations that meet these conditions. In this paper, we investigate the CPU usage trend of practical Android applications and show that many applications have method invocations suitable for the proposed dynamic CPU clock rate adjustment.

Reducing the energy consumed in the use of smart phones has become a major challenge for application developers. While this problem can be addressed at various levels, it is important to reduce the energy consumption of individual applications which can vary greatly depending on the behavior of the application. Energy profiling methods are required in order to identify the points in which the applications are consuming excessive energy and to examine how to reduce overall energy consumption by applications.