Seung Won Yoo, Korea Advanced Institute of Science and Technology (KAIST); Joontaek Oh, University of Wisconsin–Madison; Myeongin Cheon and Bonmoo Koo, Korea Advanced Institute of Science and Technology (KAIST); Wonseb Jeong, Hyunsub Song, Hyeonho Song, and Donghun Lee, Samsung Electronics; Youjip Won, Korea Advanced Institute of Science and Technology (KAIST)
In this paper, we propose DJFS, Journaling Filesystem with per-Directory Transaction. By analyzing the file access patterns in eight popular applications, we find that most file update operations are centered around the associated directory. Based upon this observation, we propose that the journaling filesystem defines the transaction in per-directory basis. DJFS consists of three key ingredients: path-based transaction selection, transaction coalescing and transaction conflict resolution. Per-directory journal transaction successfully addresses the fundamental issues associated with improving the performance of the journaling filesystem: reduce the lock contention, reduce the transaction conflict, reduce the transaction lock-up, and parallelize the journal commit. DJFS improves the throughput by 4.5× in Varmail, 2.5× in MDTest, and 3.7× in Exim, compared to the state-of-the-art journaling filesystem, FastCommit.
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author = {Seung Won Yoo and Joontaek Oh and Myeongin Cheon and Bonmoo Koo and Wonseb Jeong and Hyunsub Song and Hyeonho Song and Donghun Lee and Youjip Won},
title = {{DJFS} : {Directory-Granularity} Filesystem Journaling for {CMM-H} {SSDs}},
booktitle = {23rd USENIX Conference on File and Storage Technologies (FAST 25)},
year = {2025},
isbn = {978-1-939133-45-8},
address = {Santa Clara, CA},
pages = {35--51},
url = {https://www.usenix.org/conference/fast25/presentation/yoo},
publisher = {USENIX Association},
month = feb
}
