- lock (unlock) the address space of a process
#include <sys/mman.h> int
mlockall (int flags); int
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 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
limit and the per-process
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
is set to indicate the error.
will fail if:
Bq Er EINVAL
argument is zero, or includes unimplemented flags.
Bq Er ENOMEM
Locking the indicated range would exceed either the system or per-process
limit for locked memory.
Bq Er EAGAIN
Some or all of the memory mapped into the process's address space
could not be locked when the call was made.
Bq Er EPERM
The calling process does not have the appropriate privilege to perform
the requested operation.
functions are believed to conform to
St -p1003.1-2001 .
functions first appeared in
Fx 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
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.