MPIN(2)MPIN(2)NAME
mpin, munpin - lock pages in memory
SYNOPSIS
int mpin (void *addr, size_t);
int munpin (void *addr, size_t);
DESCRIPTIONmpin 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 super-
user 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 system-
imposed 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 memory-
mapped file, and there is insufficient space on the device
to allocate the entire file.
SEE ALSOintro(2), getrlimit(2), mlock(3C), mlockall(3C), plock(2), ulimit(2).
DIAGNOSTICS
Upon successful completion, mpin and munpin return 0. Otherwise, a value
of -1 is returned and errno is set to indicate the error.
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MPIN(2)MPIN(2)WARNING
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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