MLOCKALL (2) | System calls | Unix Manual Pages | :man▋
mlockall, munlockall - lock (unlock) the address space of a process
.In sys/mman.h int mlockall "int flags" int munlockall "void"
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 processs address space. |
| MCL_FUTURE || Lock all pages mapped into the processs 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.
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:
| || The flags argument is zero, or includes unimplemented flags. |
| || 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 processs address space could not be locked when the call was made. |
| || The calling process does not have the appropriate privilege to perform the requested operation. |
mincore(2), mlock(2), mmap(2), munmap(2), setrlimit(2)
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