lock (unlock) the address space of a process
Standard C Library (libc, -lc)
() 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
- Lock all pages currently mapped into the process's address space.
- 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
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
is set to 0
these calls are only available to the super-user. If
is set to 1 the per-process
resource limit will not be
() call unlocks any locked
memory regions in the process address space. Any regions mapped after an
() call will not be locked.
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
to indicate the error.
() will fail if:
- The flags argument is zero, or includes
- Locking the indicated range would exceed either the system or per-process
limit for locked memory.
- Some or all of the memory mapped into the process's address space could
not be locked when the call was made.
- The calling process does not have the appropriate privilege to perform the
() functions are believed to
conform to IEEE Std 1003.1-2001
() functions first appeared in
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.