| MLOCK(2) | System Calls Manual | MLOCK(2) | 
mlock, munlock —
#include <sys/mman.h>
int
  
  mlock(void
    *addr, size_t
  len);
int
  
  munlock(void
    *addr, size_t
  len);
mlock system call locks into memory the physical
  pages associated with the virtual address range starting at
  addr for len bytes. The
  munlock call unlocks pages previously locked by one or
  more mlock calls. The entire range of memory must be
  allocated.
After an mlock call, the indicated pages
    will cause neither a non-resident page nor address-translation fault until
    they are unlocked. They may still cause protection-violation faults or
    TLB-miss faults on architectures with software-managed TLBs. The physical
    pages remain in memory until all locked mappings for the pages are removed.
    Multiple processes may have the same physical pages locked via their own
    virtual address mappings. A single process may likewise have pages
    multiply-locked via different virtual mappings of the same pages or via
    nested mlock calls on the same address range.
    Unlocking is performed explicitly by munlock or
    implicitly by a call to munmap which deallocates the
    unmapped address range. Locked mappings are not inherited by the child
    process after a fork(2).
Since physical memory is a potentially scarce resource, processes
    are limited in how much they can lock down. A single process can
    mlock the minimum of a system-wide ``wired pages''
    limit and the per-process RLIMIT_MEMLOCK resource
    limit.
Portable code should ensure that the addr and len parameters are aligned to a multiple of the page size, even though the NetBSD implementation will round as necessary.
mlock() will fail if:
EAGAIN]EINVAL]ENOMEM]EPERM]mlock() was called by non-root on an architecture
      where locked page accounting is not implemented.munlock() will fail if:
mlock() and munlock()
  functions conform to IEEE Std 1003.1b-1993
  (“POSIX.1b”).
mlock() and munlock()
  functions first appeared in 4.4BSD.
| February 8, 2015 | NetBSD 9.4 |