MLOCKALL(2) OpenBSD Programmer's Manual MLOCKALL(2)NAME
mlockall, munlockall - lock (unlock) the address space of a process
SYNOPSIS
#include <sys/types.h>
#include <sys/mman.h>
int
mlockall(int flags);
int
munlockall(void);
DESCRIPTION
The 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.
The following flags affect the behavior of mlockall:
MCL_CURRENT Lock all pages currently mapped into the process's address
space.
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.
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 ``wired pages'' limit and the per-process
RLIMIT_MEMLOCK resource limit.
The munlockall call unlocks any locked memory regions in the process
address space. Any regions mapped after an munlockall call will not be
locked.
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 errno is set
to indicate the error.
ERRORSmlockall() will fail if:
[EINVAL] The flags argument is zero or includes unimplemented flags
or addr and size specify a region that would extend beyond
the end of the address space.
[ENOMEM] Locking the indicated range would exceed either the system
or per-process limit for locked memory.
[EAGAIN] Some or all of the memory mapped into the process's address
space could not be locked when the call was made.
[EPERM] The calling process does not have the appropriate
privileges to perform the requested operation.
SEE ALSOmincore(2), mlock(2), mmap(2), munmap(2), setrlimit(2)STANDARDS
The mlockall() and munlockall() functions conform to IEEE Std
1003.1b-1993 (``POSIX'').
HISTORY
The mlockall() and munlockall() functions first appeared in OpenBSD 2.9.
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.
OpenBSD 4.9 June 26, 2008 OpenBSD 4.9
