io_uring_register_ring_fd(3) — Linux manual page

NAME | SYNOPSIS | DESCRIPTION | NOTES | RETURN VALUE | SEE ALSO | COLOPHON

io_uring_register_ring_fd(3) liburing Manual io_uring_register_ring_fd(3)

NAME         top

       io_uring_register_ring_fd - register a ring file descriptor

SYNOPSIS         top

       #include <liburing.h>

       int io_uring_register_ring_fd(struct io_uring *ring);

DESCRIPTION         top

       io_uring_register_ring_fd(3) registers the file descriptor of the
       ring.

       Whenever io_uring_enter(2) is called to submit request or wait for
       completions, the kernel must grab a reference to the file
       descriptor. If the application using io_uring is threaded, the
       file table is marked as shared, and the reference grab and put of
       the file descriptor count is more expensive than it is for a non-
       threaded application.

       Similarly to how io_uring allows registration of files, this allow
       registration of the ring file descriptor itself. This reduces the
       overhead of the io_uring_enter(2) system call.

       If an application using liburing is threaded, then an application
       should call this function to register the ring descriptor when a
       ring is set up. See NOTES for restrictions when a ring is shared.

       Available since kernel 5.18.

NOTES         top

       When the ring descriptor is registered, it is stored internally in
       the struct io_uring structure. For applications that share a ring
       between threads, for example having one thread do submits and
       another reap events, then this optimization cannot be used as each
       thread may have a different index for the registered ring fd.

RETURN VALUE         top

       Returns 1 on success, indicating that one file descriptor was
       registered, or -errno on error.

SEE ALSO         top

       io_uring_unregister_ring_fd(3), io_uring_register_files(3)

COLOPHON         top

       This page is part of the liburing (A library for io_uring)
       project.  Information about the project can be found at 
       ⟨https://github.com/axboe/liburing⟩.  If you have a bug report for
       this manual page, send it to io-uring@vger.kernel.org.  This page
       was obtained from the project's upstream Git repository
       ⟨https://github.com/axboe/liburing⟩ on 2025-02-02.  (At that time,
       the date of the most recent commit that was found in the
       repository was 2025-01-22.)  If you discover any rendering
       problems in this HTML version of the page, or you believe there is
       a better or more up-to-date source for the page, or you have
       corrections or improvements to the information in this COLOPHON
       (which is not part of the original manual page), send a mail to
       man-pages@man7.org

liburing-2.2                  March 11, 2022 io_uring_register_ring_fd(3)

Pages that refer to this page: io_uring_close_ring_fd(3)io_uring_queue_init(3)io_uring_queue_init_mem(3)io_uring_queue_init_params(3)io_uring_register_ring_fd(3)io_uring_unregister_ring_fd(3)