NAME

       io_uring_register_ring_fd - register a ring file descriptor

SYNOPSIS

       #include <liburing.h>

       int io_uring_register_ring_fd(struct io_uring *ring);

DESCRIPTION

       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.

NOTES

       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

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

SEE ALSO

       io_uring_unregister_ring_fd(3), io_uring_register_files(3)