Swapping Strategy to Improve I/O Performance of Mobile Embedded Systems Using Compressed File Systems

Compressed file systems are suitable for mobile embedded systems with small capacity of storage systems because the contents of files are stored in a compressed form to save the space of storage in the compressed file systems. Therefore a data should be decompressed before it is accessed by an application program. That is a computational overhead of compressed file systems. Furthermore, the mobile embedded systems exploit demand paging mechanism to cut down their cost and size as well as the compressed file systems. And also, to extend a main memory space, the mobile embedded systems use "swapping" mechanism which stores the data evicted from a main memory in a swap area, and serves the data when the application requests it again. In this paper, we propose the new swapping strategy for the mobile embedded systems using the compressed file systems, which aims to keep the decompressed data of compressed file systems in the swap space and serves them directly from the swap space if necessary. This strategy reduces several copying overhead and decompressing operation of compressed file systems. As a result, it could improve the I/O performance of mobile embedded systems. Trace-driven simulations show that the proposed strategy performs better than existing swapping mechanism in terms of the total I/O performance, page fault ratio, and page fault latency.