Re: Latest Documentation?
Re: Latest Documentation?
- Subject: Re: Latest Documentation?
- From: Andrew Pinski <email@hidden>
- Date: Fri, 15 Feb 2002 16:07:23 -0500
Btw, mlock() is available in Darwin :)
But does the man page exist? That's the topic of
this email thread ... I haven't checked recently,
but it didn't when the memory locking topic popped
up on the coraudio-api list a few months ago.
Yes, it is a system call so it is mlock(2).
In fact it shows up when I do `man -k memory' and `man -k lock'.
Thanks,
Andrew Pinski
PS here is the man page:
MLOCK(2) System Programmer's Manual
MLOCK(2)
NAME
mlock, munlock - lock (unlock) physical pages in memory
SYNOPSIS
#include <sys/types.h>
#include <sys/mman.h>
int
mlock(caddr_t addr, size_t len)
int
munlock(caddr_t addr, size_t len)
DESCRIPTION
The 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.
For both, the addr parameter should be aligned to a multiple of the
page
size. If the len parameter is not a multiple of the page size, it
will
be rounded up to be so. The entire range must be allocated.
After an mlock call, the indicated pages will cause neither a
non-resi-
dent page nor address-translation fault until they are unlocked.
They
may still cause protection-violation faults or TLB-miss faults on
archi-
tectures 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.
RETURN VALUES
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 in-
dicates 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 in-
dicate the error.
ERRORS
Mlock() will fail if:
[EINVAL] The address given is not page aligned or the length
is neg-
ative.
[EAGAIN] Locking the indicated range would exceed either the
system
or per-process limit for locked memory.
[ENOMEM] Some portion of the indicated address range is not
allocat-
ed. There was an error faulting/mapping a page.
Munlock() will fail if:
[EINVAL] The address given is not page aligned or the length
is neg-
ative.
[ENOMEM] Some portion of the indicated address range is not
allocat-
ed. Some portion of the indicated address range is
not
locked.
SEE ALSO
fork(2), mincore(2), minherit(2), mmap(2), munmap(2),
setrlimit(2),
getpagesize(3)
BUGS
Unlike The Sun implementation, multiple mlock calls on the same
address
range require the corresponding number of munlock calls to actually
un-
lock the pages, i.e. mlock nests. This should be considered a
conse-
quence of the implementation and not a feature.
The per-process resource limit is a limit on the amount of virtual
memory
locked, while the system-wide limit is for the number of locked
physical
pages. Hence a process with two distinct locked mappings of the
same
physical page counts as 2 pages against the per-process limit and
as only
a single page in the system limit.
HISTORY
The mlock() and munlock() functions first appeared in 4.4BSD.
BSD Experimental June 2,
1993 2
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