EvFS: User-level, Event-Driven File System for Non-Volatile Memory


Takeshi Yoshimura, Tatsuhiro Chiba, and Hiroshi Horii, IBM Research–Tokyo


The extremely low latency of non-volatile memory (NVM) raises issues of latency in file systems. In particular, user-kernel context switches caused by system calls and hardware interrupts become a non-negligible performance penalty. A solution to this problem is using direct-access file systems, but existing work focuses on optimizing their non-POSIX user interfaces. In this work, we propose EvFS, our new user-level POSIX file system that directly manages NVM in user applications. EvFS minimizes the latency by building a user-level storage stack and introducing asynchronous processing of complex file I/O with page cache and direct I/O. We report that the event-driven architecture of EvFS leads to a 700-ns latency for 64-byte non-blocking file writes and reduces the latency for 4-Kbyte blocking file I/O by 20 us compared to a kernel file system with journaling disabled.

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@inproceedings {234767,
author = {Takeshi Yoshimura and Tatsuhiro Chiba and Hiroshi Horii},
title = {EvFS: User-level, Event-Driven File System for Non-Volatile Memory},
booktitle = {11th {USENIX} Workshop on Hot Topics in Storage and File Systems (HotStorage 19)},
year = {2019},
address = {Renton, WA},
url = {https://www.usenix.org/conference/hotstorage19/presentation/yoshimura},
publisher = {{USENIX} Association},
month = jul,