mlockall(3C)                                                      mlockall(3C)


NAME
     mlockall, munlockall - lock or unlock address space

SYNOPSIS
     #include <sys/mman.h>
     int mlockall(int flags);

     int munlockall(void);

DESCRIPTION
     mlockall locks all pages mapped in the address space of the calling
     process into memory, including: text, data, stack and mmaped regions.
     Locked pages are immune to all routine swapping.

     The value of flags determines whether the pages to be locked are those
     currently mapped by the address space, those that will be mapped in the
     future, or both:

               MCL_CURRENT    Lock current mappings

               MCL_FUTURE     Lock future mappings

     munlockall unlocks all memory mapped pages in the address space of the
     calling process, regardless of the number of times the pages were locked.
     Automatic memory locking of future memory mappings is disabled for the
     process.

     Locks established with mlockall are not inherited by a child process
     after a fork.

     If the address space contains autogrow regions [see mmap(2)], mlockall
     will only cause the pages through the current end of file to be locked
     down.

     In the event automatic memory locking of future mappings is enabled for a
     process (MCL_FUTURE), and the locked memory of that process stack space
     exceeds either the system's physical memory or the maximum amount of
     lockable pages per process as determined by the system variable maxlkmem,
     the process will receive a SIGSEGV with a signal code of ENOMEM [see
     sigaction(2) and signal(5)]. If the locked memory of the process heap
     space exceeds either the system's physical memory or the maximum amount
     of lockable pages per process maxlkmem, the system call which attempts
     the expansion will fail without making a change to the amount of
     allocated space, and errno is set to ENOMEM.

     mlockall or munlockall will fail if one or more of the following are
     true:

     [EAGAIN]    There was insufficient lockable memory to lock the entire
                 address space.  This may occur even though the amount
                 requested was less than the system-imposed maximum number of
                 locked pages.


     [EBUSY]     munlockall will fail with this error if a region of the
                 address space has some active I/O initiated by some other
                 process belonging to same share group.

     [EINVAL]    The flags argument is zero or contains invalid flags.

     [ENOMEM]    The caller was not super-user and the number of pages to be
                 locked exceeded the maximum number of lockable pages per
                 process as defined by the system variable maxlkmem [see
                 systune(1M)].

     [ENOMEM]    The total number of pages locked by the caller would exceed
                 the maximum resident size for the process [see setrlimit(2)].

     [ENOSPC]    The address space of the calling process contains a memory-
                 mapped file, and there is insufficient space on the device to
                 allocate the entire file.

SEE ALSO
     exec(2), exit(2), fork(2), mmap(2), mlock(3C), munlock(3C), mpin(2),
     munpin(2), plock(2), sigaction(2), sysconf(3C)

DIAGNOSTICS
     Upon successful completion, the functions mlockall and munlockall return
     0, otherwise, they return -1 and set errno to indicate the error.

WARNING
     The mlockall/munlockall pair and the plock function provide similar
     functionality. Developers should choose the set that best suites their
     application and stick with it, as mixing the interfaces may result in
     unexpected behavior.


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