mlockall(3)mlockall(3)NAME
mlockall, munlockall - Locks into memory, or unlocks, all of a speci‐
fied process's pages (P1003.1b)
SYNOPSIS
#include <sys/mman.h>
int mlockall ( int options);
int munlockall (void);
LIBRARY
Realtime Library (librt.so, librt.a)
PARAMETERS
Determines whether the pages to be locked are those currently mapped by
the process's address space, those that will be mapped in the future,
or both. The options argument is constructed as the OR of one or more
of the constants, MCL_CURRENT or MCL_FUTURE, as defined in the <mman.h>
header file.
DESCRIPTION
The mlockall function causes all of the pages mapped by the process's
address space to be memory resident until unlocked by a call to the
munlockall function, until the process exits, or until the process
calls exec. MCL_CURRENT locks all of the pages currently mapped into
the process's address space. MCL_FUTURE locks all of the pages that
become mapped into the process's address space in the future, when
those mappings are established. You can specify MCL_CURRENT and subse‐
quently specify MCL_FUTURE to lock both current and future address
space.
The munlockall function unlocks all currently mapped pages of the
process's address space. Any pages that become mapped into a process's
address space after a call to munlockall are not locked unless other‐
wise specified by a subsequent call to mlockall. Pages locked or mapped
into another process's address space are unaffected by this process's
call to the munlockall function.
Locking the process's pages into memory also makes the process unswap‐
pable.
When the pages are unlocked, the process is made swappable.
A lock is not inherited across a fork. All memory locks established on
an address by this process are removed if an address range associated
with the lock is unmapped with a call to the munmap function.
You must have superuser privileges to call the mlockall function.
RETURN VALUES
On a successful call to the mlockall function, a value of 0 (zero) is
returned and memory is locked. On an unsuccessful call, a value of -1
is returned, no memory is locked, and errno is set to indicate that an
error occurred.
On a successful call to the munlockall function, a value of 0 (zero) is
returned and memory is unlocked. On an unsuccessful call, a value of -1
is returned and errno is set to indicate that an error occurred.
ERRORS
The mlockall and munlockall functions fail under the following condi‐
tion: The implementation does not support this memory locking inter‐
face.
If any of the following conditions occur, the mlockall function fails:
Some or all of the memory identified by the operation could not be
locked when the call was made. The options argument is zero or
includes unimplemented options. Locking all of the pages currently
mapped into the process's address space exceeds an implementation-
defined limit on the amount of memory that the process may lock. The
calling process does not have the appropriate privilege to perform the
requested operation.
SEE ALSO
Functions: exec(2), _exit(2), fork(2), munmap(2)
Guide to Realtime Programming
mlockall(3)
