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MLOCKALL(2)		      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 associ-
       ated with the address space of a	process	until the address space	is un-
       locked, 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 map-
		    pings 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  unimple-
			  mented 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	physi-
       cal 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	13.2			 May 13, 2019			   MLOCKALL(2)
NAME | LIBRARY | SYNOPSIS | DESCRIPTION | RETURN VALUES | ERRORS | SEE ALSO | STANDARDS | HISTORY | BUGS

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