Characterization and Throttling-Based Mitigation of Memory Interference for Heterogeneous Smartphones

The availability of a wide range of general purpose as well as accelerator cores on modern smart phones means that a significant number of applications can be executed on a smart phone simultaneously, resulting in an ever increasing demand on the memory subsystem. While the increased computation capability is intended for improving user experience, memory requests from each concurrent application exhibit unique memory access patterns as well as specific timing constraints. If not considered, this could lead to significant memory contention and result in lowered user experience. In this paper, we design experiments to analyze the performance degradation caused by the interference at the memory subsystem for a broad range of commonly-used smart phone applications. The characterization studies are performed on a real smart phone device -- Google Nexus5 -- running an Android operating system. Our results show that user-centric smart phone applications, such as web browsing and media player, suffer up to 34% and 21% performance degradation, respectively, from shared resource contention at the application processor's last-level cache, the communication fabric, and the main memory. Taking a step further, we demonstrate the feasibility and effectiveness of a frequency throttling-based memory interference mitigation technique. At the expense of performance degradation of interfering applications, frequency throttling is an effective technique for mitigating memory interference, leading to better QoS and user experience, for user-centric applications.