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.\" Copyright (C) 2022 Jens Axboe <axboe@kernel.dk> .\" .\" SPDX-License-Identifier: LGPL-2.0-or-later .\" .TH io_uring_register_ring_fd 3 "March 11, 2022" "liburing-2.2" "liburing Manual" .SH NAME io_uring_register_ring_fd \- register a ring file descriptor .SH SYNOPSIS .nf .B #include <liburing.h> .PP .BI "int io_uring_register_ring_fd(struct io_uring *" ring ");" .fi .SH DESCRIPTION .PP .BR io_uring_register_ring_fd (3) registers the file descriptor of the ring. Whenever .BR 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 .BR 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. .SH NOTES When the ring descriptor is registered, it is stored internally in the .I 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. .SH RETURN VALUE Returns 1 on success, indicating that one file descriptor was registered, or .BR -errno on error. .SH SEE ALSO .BR io_uring_unregister_ring_fd (3), .BR io_uring_register_files (3)
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13 entries across 13 versions & 1 rubygems