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.\" $OpenBSD: mlockall.2,v 1.10 2019/01/11 18:46:30 deraadt Exp $
.\" $NetBSD: mlockall.2,v 1.6 2000/06/26 17:00:02 kleink Exp $
.\"
.\" Copyright (c) 1999 The NetBSD Foundation, Inc.
.\" All rights reserved.
.\"
.\" This code is derived from software contributed to The NetBSD Foundation
.\" by Jason R. Thorpe of the Numerical Aerospace Simulation Facility,
.\" NASA Ames Research Center.
.\"
.\" Redistribution and use in source and binary forms, with or without
.\" modification, are permitted provided that the following conditions
.\" are met:
.\" 1. Redistributions of source code must retain the above copyright
.\" notice, this list of conditions and the following disclaimer.
.\" 2. Redistributions in binary form must reproduce the above copyright
.\" notice, this list of conditions and the following disclaimer in the
.\" documentation and/or other materials provided with the distribution.
.\"
.\" THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS
.\" ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
.\" TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
.\" PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS
.\" BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
.\" CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
.\" SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
.\" INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
.\" CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
.\" ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
.\" POSSIBILITY OF SUCH DAMAGE.
.\"
.Dd $Mdocdate: January 11 2019 $
.Dt MLOCKALL 2
.Os
.Sh NAME
.Nm mlockall ,
.Nm munlockall
.Nd lock (unlock) the address space of a process
.Sh SYNOPSIS
.In sys/mman.h
.Ft int
.Fn mlockall "int flags"
.Ft int
.Fn munlockall "void"
.Sh DESCRIPTION
The
.Fn mlockall
system call locks into memory the physical pages associated with the
address space of a process until the address space is unlocked, the
process exits, or execs another program image.
.Pp
The following flags affect the behavior of
.Fn mlockall :
.Bl -tag -width MCL_CURRENT
.It Dv MCL_CURRENT
Lock all pages currently mapped into the process's address space.
.It Dv MCL_FUTURE
Lock all pages mapped into the process's address space in the future,
at the time the mapping is established.
Note that this may cause future mappings to fail if those mappings
cause resource limits to be exceeded.
.El
.Pp
Since physical memory is a potentially scarce resource, processes are
limited in how much they can lock down.
A single process can lock the minimum of a system-wide
.Dq wired pages
limit and the per-process
.Dv RLIMIT_MEMLOCK
resource limit.
.Pp
The
.Fn munlockall
call unlocks any locked memory regions in the process address space.
Any regions mapped after an
.Fn munlockall
call will not be locked.
.Sh RETURN VALUES
.Rv -std mlockall munlockall
.Sh ERRORS
.Fn mlockall
will fail if:
.Bl -tag -width Er
.It Bq Er EINVAL
The
.Fa flags
argument is zero or includes unimplemented flags.
.It Bq Er ENOMEM
Locking all of the pages currently mapped would exceed either
the system or per-process
limit for locked memory.
.It Bq Er EAGAIN
Some or all of the memory mapped into the process's address space
could not be locked when the call was made.
.It Bq Er EPERM
The calling process does not have the appropriate privileges to perform
the requested operation.
.El
.Sh SEE ALSO
.Xr mlock 2 ,
.Xr mmap 2 ,
.Xr munmap 2 ,
.Xr setrlimit 2
.Sh STANDARDS
The
.Fn mlockall
and
.Fn munlockall
functions conform to
.St -p1003.1-2008 .
.Sh HISTORY
The
.Fn mlockall
and
.Fn munlockall
functions first appeared in
.Ox 2.9 .
.Sh BUGS
The per-process resource limit is a limit on the amount of virtual
memory locked, while the system-wide limit is for the number of locked
physical pages.
Hence a process with two distinct locked mappings of the same physical page
counts as 2 pages against the per-process limit and only as a single page
in the system limit.
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