MLOCKALL(2)               FreeBSD System Calls Manual              MLOCKALL(2)

NAME
     mlockall, munlockall - lock (unlock) the address space of a process

LIBRARY
     Standard C Library (libc, -lc)

SYNOPSIS
     #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 vm.max_user_wired and the
     per-process RLIMIT_MEMLOCK resource limit.

     If security.bsd.unprivileged_mlock is set to 0 these calls are only
     available to the super-user.  If vm.old_mlock is set to 1 the per-process
     RLIMIT_MEMLOCK resource limit will not be applied for mlockall() calls.

     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.

ERRORS
     mlockall() will fail if:

     [EINVAL]           The flags argument is zero, or includes unimplemented
                        flags.

     [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
                        privilege to perform the requested operation.

SEE ALSO
     mincore(2), mlock(2), mmap(2), munmap(2), setrlimit(2)

STANDARDS
     The mlockall() and munlockall() functions are believed to conform to IEEE
     Std 1003.1-2001 ("POSIX.1").

HISTORY
     The mlockall() and munlockall() functions first appeared in FreeBSD 5.1.

BUGS
     The per-process and system-wide resource limits of locked memory apply to
     the amount of virtual memory locked, not the amount of locked physical
     pages.  Hence two distinct locked mappings of the same physical page
     counts as 2 pages aginst the system limit, and also against the per-
     process limit if both mappings belong to the same physical map.

FreeBSD 13.1-RELEASE-p6          May 13, 2019          FreeBSD 13.1-RELEASE-p6