Io uring: Difference between revisions

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io_uring (previously known as aioring) is a Linux kernel system call interface for storage device asynchronous I/O operations addressing performance issues with similar interfaces provided by functions like read()/write() or aio_read()/aio_write() etc. for operations on data accessed by file descriptors.^[1]^[2]^: 2

It was primarily developed by Jens Axboe at Facebook.^[1]

Interface

Internally it works by creating two buffers dubbed as "queue rings" (circular buffers) for storage of submission and completion of I/O requests (for storage devices, submission queue (SQ) and completion queue (CQ) respectively).^[3] Keeping these buffers shared between the kernel and application helps to boost the I/O performance by eliminating the need to issue extra and expensive system calls to copy these buffers between the two.^[1]^[4]^[3] According to the io_uring design paper, the SQ buffer is writable only by consumer application, and the CQ buffer only by the kernel.^[1]^: 3

The API provided by liburing library for userspace (applications) can be used to interact with the kernel interface more easily.^[1]^[1]^: 12

Both kernel interface and library were adopted in Linux 5.1 kernel version.^[1]^[4]^[5]

The Linux kernel has had asynchronous I/O since version 2.5, but it was seen as difficult to use and inefficient.^[6] The old API only supported certain niche use cases.^[7]

References

^ ^a ^b ^c ^d ^e ^f ^g "Linux Kernel Getting io_uring To Deliver Fast & Efficient I/O - Phoronix". Phoronix. Retrieved 2021-03-14.{{cite web}}: CS1 maint: url-status (link)
^ Axboe, Jens (October 15, 2019). "Efficient IO with io_uring" (PDF).{{cite web}}: CS1 maint: url-status (link)
^ ^a ^b "Getting Hands-on with io_uring using Go". developers.mattermost.com. Retrieved 2021-11-20.
^ ^a ^b "The rapid growth of io_uring [LWN.net]". lwn.net. Retrieved 2021-11-20.
^ "Faster IO through io_uring | Kernel Recipes 2019". Retrieved 2021-03-14.
^ Corbet, Jonathan. "Ringing in a new asynchronous I/O API". LWN.net. Retrieved 2021-03-14.{{cite web}}: CS1 maint: url-status (link)
^ "What's new with io_uring" (PDF). Retrieved 2022-06-01.

External links

Efficient I/O with io_uring, in-depth description of motivation behind io_uring, interface (data structures etc.), and performance assessment
liburing source repository
io_uring source directory in the Linux kernel repository

[Axboe2019-1] ^ ^a ^b ^c ^d ^e ^f ^g "Linux Kernel Getting io_uring To Deliver Fast & Efficient I/O - Phoronix". Phoronix. Retrieved 2021-03-14.{{cite web}}: CS1 maint: url-status (link)

[2] Axboe, Jens (October 15, 2019). "Efficient IO with io_uring" (PDF).{{cite web}}: CS1 maint: url-status (link)

[:1-3] "Getting Hands-on with io_uring using Go". developers.mattermost.com. Retrieved 2021-11-20.

[:0-4] "The rapid growth of io_uring [LWN.net]". lwn.net. Retrieved 2021-11-20.

[5] "Faster IO through io_uring | Kernel Recipes 2019". Retrieved 2021-03-14.

[6] Corbet, Jonathan. "Ringing in a new asynchronous I/O API". LWN.net. Retrieved 2021-03-14.{{cite web}}: CS1 maint: url-status (link)

[7] "What's new with io_uring" (PDF). Retrieved 2022-06-01.

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 == External links ==
 * [https://kernel.dk/io_uring.pdf Efficient I/O with io_uring], in-depth description of motivation behind io_uring, interface (data structures etc.), and performance assessment
-* [https://git.kernel.dk/cgit/liburing/ {{Code|liburing}} source repository]
+* [https://git.kernel.dk/cgit/liburing/tree/ {{Code|liburing}} source repository]
 * [https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/io_uring {{Code|io_uring}} source directory in the Linux kernel repository]