.\" Copyright (C) 2025 Jens Axboe <axboe@kernel.dk>
.\"
.\" SPDX-License-Identifier: LGPL-2.0-or-later
.\"
.TH io_uring_mlock_size 3 "January 18, 2025" "liburing-2.4" "liburing Manual"
.SH NAME
io_uring_mlock_size \- get required memlock size for a ring
.SH SYNOPSIS
.nf
.B #include <liburing.h>
.PP
.BI "ssize_t io_uring_mlock_size(unsigned " entries ", unsigned " flags ");"
.fi
.SH DESCRIPTION
.PP
The
.BR io_uring_mlock_size (3)
function returns the required
.B RLIMIT_MEMLOCK
memory size for an io_uring ring with
.I entries
entries and the specified setup
.IR flags .

On newer kernels (5.12+), io_uring no longer requires any memlock memory
and this function will return 0. On older kernels (5.11 and prior), this
returns the required memory so that the caller can ensure that enough
.B RLIMIT_MEMLOCK
space is available before setting up a ring.

For more control over the ring parameters, use
.BR io_uring_mlock_size_params (3)
instead.

.SH RETURN VALUE
Returns the required memlock size in bytes on success, 0 if no memlock
is needed, or a negative errno value on error.
.SH SEE ALSO
.BR io_uring_mlock_size_params (3),
.BR io_uring_memory_size (3),
.BR io_uring_queue_init (3),
.BR getrlimit (2)