Title: Improved Doubly-Circular Buffer Structure for EXT4 Journaling File System to Increase Performance on NAND Flash

Year of Publication: Feb - 2016
Page Numbers: 18-24
Authors: Teaseung Kim, Kyongsok Kim
Conference Name: The International Conference on Innovations in Intelligent Systems and Computing Technologies (ICIISCT2016)
- Philippines


Recently smart devices based on Android, one of operating systems, are widely used by many users. Such Android-based smart devices use NAND flash memory as storage media. In contrast to other file systems, EXT4 file system of Android has journaling feature. Simple Circular Buffer Structure and Algorithm used by journal feature does not cause performance degradation on hard disks. However, the authors found that, due to the characteristics of journal recording algorithm, performance of that journaling feature degrades on NAND flash memory. Specifically VPC (Valid Page Copy) occurs quite frequently. In this paper, the authors propose Doubly-Circular Buffer Structure and Algorithm to replace the Simple Circular Buffer Structure and Algorithm which causes performance degradation on NAND flash memory. Specifically, by deleting Journal Cold Pages early that will not be used later, we can reduce unnecessary VPCs and therefore improve the performance of smart devices using EXT4 file system on NAND flash memory.