I/O Passthru: Upstreaming a flexible and efficient I/O Path in Linux


Kanchan Joshi, Anuj Gupta, Javier González, Ankit Kumar, Krishna Kanth Reddy, Arun George, and Simon Lund, Samsung Semiconductor; Jens Axboe, Meta Platforms Inc.


New storage interfaces continue to emerge fast on Non-Volatile Memory Express (NVMe) storage. Fitting these innovations in the general-purpose I/O stack of operating systems has been challenging and time-consuming. The NVMe standard is no longer limited to block-I/O, but the Linux I/O advances historically centered around the block-I/O path. The lack of scalable OS interfaces risks the adoption of the new storage innovations.

We introduce I/O Passthru, a new I/O Path that has made its way into the mainline Linux Kernel. The key ingredients of this new path are NVMe char interface and io_uring command. In this paper, we present our experience building and upstreaming I/O Passthru and report on how this helps to consume new NVMe innovations without changes to the Linux kernel. We provide experimental results to (i) compare its efficiency against existing io_uring block path and (ii) demonstrate its flexibility by integrating data placement into Cachelib. FIO peak performance workloads show 16–40% higher IOPS than block path.

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@inproceedings {294787,
author = {Kanchan Joshi and Anuj Gupta and Javier Gonzalez and Ankit Kumar and Krishna Kanth Reddy and Arun George and Simon Lund and Jens Axboe},
title = {{I/O} Passthru: Upstreaming a flexible and efficient {I/O} Path in Linux},
booktitle = {22nd USENIX Conference on File and Storage Technologies (FAST 24)},
year = {2024},
isbn = {978-1-939133-38-0},
address = {Santa Clara, CA},
pages = {107--121},
url = {https://www.usenix.org/conference/fast24/presentation/joshi},
publisher = {USENIX Association},
month = feb

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