The
mlockall 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
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 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 “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 locked.