mlockall (2)

Leading comments

	$NetBSD: mlockall.2,v 1.11 2003/04/16 13:34:54 wiz Exp $

 Copyright (c) 1999 The NetBSD Foundation, Inc.
 All rights reserved.

 This code is derived from software contributed to The NetBSD Foundation
 by Jason R. Thorpe of the Numerical Aerospace Simulation Facility,
 NASA Ames Research Center.

 Redistribution and use in source and binary forms, with or without
 modification, are permitted provided that the following conditions
 are met:
 1. Redistributions of source code must retain the ...

(The comments found at the beginning of the groff file "man2/mlockall.2freebsd".)

NAME

mlockall munlockall - lock (unlock) the address space of a process

LIBRARY

Lb libc

SYNOPSIS

In sys/mman.h Ft int Fn mlockall int flags Ft int Fn munlockall void

DESCRIPTION

The Fn 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 Fn mlockall :

MCL_CURRENT

Lock all pages currently mapped into the process's address space.

MCL_FUTURE

Lock all pages mapped into the process's 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 vm.max_wired and the per-process RLIMIT_MEMLOCK resource limit.

If security.bsd.unprivileged_mlock is set to 0 these calls are only available to the super-user. If vm.old_mlock is set to 1 the per-process RLIMIT_MEMLOCK resource limit will not be applied for Fn mlockall calls.

The Fn munlockall call unlocks any locked memory regions in the process address space. Any regions mapped after an Fn munlockall call will not be locked.

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 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.

ERRORS

Fn mlockall will fail if:

Bq Er EINVAL

The Fa flags argument is zero, or includes unimplemented flags.

Bq Er ENOMEM

Locking the indicated range would exceed either the system or per-process limit for locked memory.

Bq Er EAGAIN

Some or all of the memory mapped into the process's address space could not be locked when the call was made.

Bq Er EPERM

The calling process does not have the appropriate privilege to perform the requested operation.

SEE ALSO

mincore(2), mlock(2), mmap(2), munmap(2), setrlimit(2)

STANDARDS

The Fn mlockall and Fn munlockall functions are believed to conform to St -p1003.1-2001 .

HISTORY

The Fn mlockall and Fn munlockall functions first appeared in Fx 5.1 .

BUGS

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.