Exploiting write-only-once characteristics of file data in smartphone buffer cache management

In this article, we analyze file access characteristics of smartphone applications and find out that a large portion of file data in smartphones are written only once. This specific phenomenon appears due to the behavior of SQLite, a lightweight database library used in most smartphone applications. Based on this observation, we present a new buffer cache management scheme for smartphone systems that considers non-reusability of write-only-once data that we observe. Buffer cache improves file access performances by maintaining hot data in memory thereby servicing subsequent requests without storage accesses. The proposed scheme classifies write-only-once data and aggressively evicts them from the buffer cache to improve cache space utilization. Experimental results with various real smartphone applications show that the proposed buffer cache management scheme improves the performance of smartphone buffer cache by 5%-33%. We also show that our scheme can reduce the buffer cache size to 1/4 of the original system without performance degradation, which allows the reduction of energy consumption in a smartphone memory system by 27%-92%.