7bdf80e571
in a bunch of man pages. Use the correct .Bx (BSD UNIX) or .At (AT&T UNIX) macros instead of explicitly specifying the version in the text in a bunch of man pages.
163 lines
5.3 KiB
Groff
163 lines
5.3 KiB
Groff
.\" Copyright (c) 1993
|
|
.\" The Regents of the University of California. All rights reserved.
|
|
.\"
|
|
.\" 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.
|
|
.\" 3. All advertising materials mentioning features or use of this software
|
|
.\" must display the following acknowledgement:
|
|
.\" This product includes software developed by the University of
|
|
.\" California, Berkeley and its contributors.
|
|
.\" 4. Neither the name of the University nor the names of its contributors
|
|
.\" may be used to endorse or promote products derived from this software
|
|
.\" without specific prior written permission.
|
|
.\"
|
|
.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS 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 REGENTS 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.
|
|
.\"
|
|
.\" @(#)mlock.2 8.2 (Berkeley) 12/11/93
|
|
.\"
|
|
.Dd June 2, 1993
|
|
.Dt MLOCK 2
|
|
.Os
|
|
.Sh NAME
|
|
.Nm mlock ,
|
|
.Nm munlock
|
|
.Nd lock (unlock) physical pages in memory
|
|
.Sh SYNOPSIS
|
|
.Fd #include <sys/types.h>
|
|
.Fd #include <sys/mman.h>
|
|
.Ft int
|
|
.Fn mlock "caddr_t addr" "size_t len"
|
|
.Ft int
|
|
.Fn munlock "caddr_t addr" "size_t len"
|
|
.Sh DESCRIPTION
|
|
The
|
|
.Fn mlock
|
|
system call
|
|
locks into memory the physical pages associated with the virtual address
|
|
range starting at
|
|
.Fa addr
|
|
for
|
|
.Fa len
|
|
bytes.
|
|
The
|
|
.Fn munlock
|
|
call unlocks pages previously locked by one or more
|
|
.Fn mlock
|
|
calls.
|
|
For both, the
|
|
.Fa addr
|
|
parameter should be aligned to a multiple of the page size.
|
|
If the
|
|
.Fa len
|
|
parameter is not a multiple of the page size, it will be rounded up
|
|
to be so.
|
|
The entire range must be allocated.
|
|
.Pp
|
|
After an
|
|
.Fn mlock
|
|
call, the indicated pages will cause neither a non-resident page
|
|
nor address-translation fault until they are unlocked.
|
|
They may still cause protection-violation faults or TLB-miss faults on
|
|
architectures with software-managed TLBs.
|
|
The physical pages remain in memory until all locked mappings for the pages
|
|
are removed.
|
|
Multiple processes may have the same physical pages locked via their own
|
|
virtual address mappings.
|
|
A single process may likewise have pages multiply-locked via different virtual
|
|
mappings of the same pages or via nested
|
|
.Fn mlock
|
|
calls on the same address range.
|
|
Unlocking is performed explicitly by
|
|
.Fn munlock
|
|
or implicitly by a call to
|
|
.Fn munmap
|
|
which deallocates the unmapped address range.
|
|
Locked mappings are not inherited by the child process after a
|
|
.Xr fork 2 .
|
|
.Pp
|
|
Since physical memory is a potentially scarce resource, processes are
|
|
limited in how much they can lock down.
|
|
A single process can
|
|
.Fn mlock
|
|
the minimum of
|
|
a system-wide ``wired pages'' limit and
|
|
the per-process
|
|
.Li RLIMIT_MEMLOCK
|
|
resource limit.
|
|
.Sh RETURN VALUES
|
|
A return value of 0 indicates that the call
|
|
succeeded and all pages in the range have either been locked or unlocked.
|
|
A return value of -1 indicates an error occurred and the locked
|
|
status of all pages in the range remains unchanged.
|
|
In this case, the global location
|
|
.Va errno
|
|
is set to indicate the error.
|
|
.Sh ERRORS
|
|
.Fn Mlock
|
|
will fail if:
|
|
.Bl -tag -width Er
|
|
.It Bq Er EINVAL
|
|
The address given is not page aligned or the length is negative.
|
|
.It Bq Er EAGAIN
|
|
Locking the indicated range would exceed either the system or per-process
|
|
limit for locked memory.
|
|
.It Bq Er ENOMEM
|
|
Some portion of the indicated address range is not allocated.
|
|
There was an error faulting/mapping a page.
|
|
.El
|
|
.Fn Munlock
|
|
will fail if:
|
|
.Bl -tag -width Er
|
|
.It Bq Er EINVAL
|
|
The address given is not page aligned or the length is negative.
|
|
.It Bq Er ENOMEM
|
|
Some portion of the indicated address range is not allocated.
|
|
Some portion of the indicated address range is not locked.
|
|
.El
|
|
.Sh "SEE ALSO"
|
|
.Xr fork 2 ,
|
|
.Xr mmap 2 ,
|
|
.Xr munmap 2 ,
|
|
.Xr setrlimit 2 ,
|
|
.Xr getpagesize 3
|
|
.Sh BUGS
|
|
Unlike The Sun implementation, multiple
|
|
.Fn mlock
|
|
calls on the same address range require the corresponding number of
|
|
.Fn munlock
|
|
calls to actually unlock the pages, i.e.
|
|
.Fn mlock
|
|
nests.
|
|
This should be considered a consequence of the implementation
|
|
and not a feature.
|
|
.Pp
|
|
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 as only a single page
|
|
in the system limit.
|
|
.Sh HISTORY
|
|
The
|
|
.Fn mlock
|
|
and
|
|
.Fn munlock
|
|
functions first appeared in
|
|
.Bx 4.4 .
|