MPIN(2) MPIN(2)
mpin, munpin - lock pages in memory
int mpin (void *addr, size_t);
int munpin (void *addr, size_t);
mpin reads into memory all pages over the range (addr, addr + len), and
locks the pages into memory. Associated with each locked page is a
counter which is incremented each time the page is locked. The superuser
can lock as many pages as it wishes, other users are limited to a
configurable per process maximum.
munpin decrements the lock counter associated with the pages over the
range (addr, addr + len). Pages whose counters are zero are available to
be swapped out at the system's discretion.
mpin or munpin will fail if one or more of the following are true:
[EINVAL] The addresses specified by (addr, addr + len) are not
mapped into the user's address space.
[EAGAIN] There was insufficient lockable memory to lock the entire
address range (addr, addr + len). This may occur even
though the amount requested was less than the systemimposed
maximum number of locked pages.
[EBUSY] munpin will fail with this error if the address range
specified has some active I/O initiated by some other
process belonging to same share group.
[ENOMEM] The caller was not super-user and the number of pages to
be locked exceeded the per process limit {PLOCK_MAX} [see
intro(2)].
[ENOMEM] The total number of pages locked by the caller would
exceed the maximum resident size for the process [see
setrlimit(2)].
[ENOSPC] The address range (addr, addr + len) contains a memorymapped
file, and there is insufficient space on the device
to allocate the entire file.
intro(2), getrlimit(2), mlock(3C), mlockall(3C), plock(2), ulimit(2).
Upon successful completion, mpin and munpin return 0. Otherwise, a value
of -1 is returned and errno is set to indicate the error.
Page 1
MPIN(2) MPIN(2)
The functions mpin/munpin and mlock/munlock provide similar
functionality. The major difference between the two sets is that
mpin/munpin maintains a per page lock counter and mlock/munlock does not.
Developers should choose the set that best suites their application and
stick with it, as mixing the interfaces may result in unexpected
behavior.
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