CEIU: Consistent and Efficient Incremental Update mechanism for mobile systems on flash storage

The ever-growing sizes and frequent updating of mobile applications cause high network and storage cost for updating. Hence, emerging mobile systems often employ incremental update algorithms, typically HDiffPatch, to upgrade mobile applications. However, we find that existing incremental update algorithms not only generate a significant amount of redundant data accesses, but also lacks of consistency guarantees for the whole package of application. In this paper, we present a novel Consistent and Efficient Incremental Update (CEIU) mechanism for upgrading mobile applications. Firstly, CEIU reduces the memory consumption and file access of incremental updates by reusing the indexes of blocks in the old image rather than copying the blocks. Secondly, CEIU employs a two-level journaling mechanism to ensure the consistency of the whole package and subfiles of the new image. We implement the proposed mechanism in Linux kernel based on TI-LFAT file system and evaluate it with real-world applications. The experimental results show that the proposed mechanism can reduce 30%–80% memory footprints in comparison with HDiffPatch, the state-of-the-art incremental update algorithm. It also significantly reduces the recovery time when power failure or system crash occurs.