A Compressed File System Manager for Flash Memory Based Consumer Electronics Devices

NAND flash memory is widely used as secondary storage in portable consumer electronics devices such as smartphones and digital cameras. These devices often employ a compressed file system to efficiently manage the limited storage space. However, retrieving data from a compressed file system incurs substantial delays in launching applications due to additional decompression procedures at run time. This paper presents an efficient compressed file system manager (CFSM) that reduces the application launch time in portable consumer electronics devices. CFSM uses two novel techniques. One is the selective decompression that reduces the user-perceived latency by decompressing only the actually requested data acquired by a bulk read. The other technique is cost-aware replacement that preferentially evicts data from uncompressed file systems when memory is full because they are quicker to access than compressed data. A prototype of CFSM has been implemented on the Linux operating system. Measurement studies show that CFSM reduces the application launch latency by 28% on average compared to the well-known CramFS compressed file system(1).