mlockall man page on FreeBSD

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MLOCKALL(2)		    BSD System Calls Manual		   MLOCKALL(2)

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

     Standard C Library (libc, -lc)

     #include <sys/mman.h>

     mlockall(int flags);


     The mlockall() system call locks into memory the physical pages associ‐
     ated 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

     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 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

     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.

     mlockall() will fail if:

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

     [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

     [EPERM]		The calling process does not have the appropriate
			privilege to perform the requested operation.

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

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

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

     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 as only
     a single page in the system limit.

BSD				 June 12, 1999				   BSD

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