Understanding the impact of number of CPU cores on user satisfaction in smartphones

Understanding user experience/satisfaction with mobile systems in order to manage computational resources has become a popular approach in recent years. One of the key challenges in this area is how to gauge user satisfaction. In this paper, we study the impact of CPU configuration on user satisfaction and power consumption with real users. Specifically, we propose a system to save energy by altering active CPU core count and frequency while keeping users satisfied. The system utilizes user-facing metrics such as frame rate and input lag to predict user satisfaction and then configure CPU core count and frequency in real-time to maximize satisfaction while minimizing power consumption. We first study a set of applications in-the-lab and show that we can accurately model satisfaction with the collected user-facing metrics. We then go into-the-wild in order to evaluate the proposed system in real environments. In the wild, we build a user-independent (user-oblivious) and user-dependent (personal) model. Users test the two models and the default scheme for one-week duration, which composes 140 days of worth of data. When compared to default scheme, our results show that, without impacting satisfaction, user-independent and user-dependent models save 12.3% and 11.8% of total system energy on average, respectively.