Integrated Host-SSD Mapping Table Management for Improving User Experience of Smartphones.

Host Performance Booster (HPB) was proposed to improve the performance of high-capacity mobile flash storage systems by utilizing unused host DRAM memory. In this paper, we investigate how HPB should be managed so that the user experience of smartphones can be enhanced from HPB-enabled high-performance mobile storage systems. From our empirical study on Android environments, we identified two requirements for an efficient HPB management scheme in smartphones. First, HPB should be managed in a foreground app-centric manner so that the user-perceived latency can be greatly reduced. Second, the capacity of the HPB memory should be dynamically adjusted so as not to degrade the user experience of the foreground app. As an efficient HPB management solution that meets the identified requirements, we propose an integrated host-SSD mapping table management scheme, HPBvalve, for smartphones. HPBvalve prioritizes the foreground app in managing mapping table entries in the HPB memory. HPBvalve dynamically resizes the overall capacity of the HPB memory depending on the memory pressure status of the smartphone. Our experimental results using the prototype implementation demonstrate that HPBvalve improves UX-critical app launching time by up to 43% (250 ms) over the existing HPB management scheme, without negatively affecting memory pressure. Meanwhile, the L2P mapping misses are alleviated by up to 78%.