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A full-system approach to analyze the impact of next-generation mobile flash storage

As mobile devices gain ever more capabilities, their software and hardware complexity increases. Full system performance generally depends on complex hardware/software interactions, making it hard to reason about the performance impact of new components. These challenges are especially prominent for the flash storage as it involves a complex hardware architecture, and an extensive software stack. Universal Flash Storage (UFS) is an emerging flash interface proposed to address the growing demands of mobile workloads. However, due to the complexity of the system it is hard to determine the contribution of the storage device on the performance perceived by the user. To study the flash storage impact on modern mobile systems, and evaluate next-generation flash devices, we introduce a detailed UFS device model in the open-source full-system simulator gem5. We show the impact of different-performing flash devices on real mobile workloads, and compare the result with existing systems. Contrary to claims made by related work, we show that web browsing performance in itself is independent of the flash performance, but that tasks heavily utilizing the flash storage are clearly seeing the benefits of UFS. Our work enables performance analysis in both the hardware and the software layers of the storage system, and thus provides a platform for further research into mobile flash storage.