54a3a11421
Historically we have not distinguished between kernel wirings and user wirings for accounting purposes. User wirings (via mlock(2)) were subject to a global limit on the number of wired pages, so if large swaths of physical memory were wired by the kernel, as happens with the ZFS ARC among other things, the limit could be exceeded, causing user wirings to fail. The change adds a new counter, v_user_wire_count, which counts the number of virtual pages wired by user processes via mlock(2) and mlockall(2). Only user-wired pages are subject to the system-wide limit which helps provide some safety against deadlocks. In particular, while sources of kernel wirings typically support some backpressure mechanism, there is no way to reclaim user-wired pages shorting of killing the wiring process. The limit is exported as vm.max_user_wired, renamed from vm.max_wired, and changed from u_int to u_long. The choice to count virtual user-wired pages rather than physical pages was done for simplicity. There are mechanisms that can cause user-wired mappings to be destroyed while maintaining a wiring of the backing physical page; these make it difficult to accurately track user wirings at the physical page layer. The change also closes some holes which allowed user wirings to succeed even when they would cause the system limit to be exceeded. For instance, mmap() may now fail with ENOMEM in a process that has called mlockall(MCL_FUTURE) if the new mapping would cause the user wiring limit to be exceeded. Note that bhyve -S is subject to the user wiring limit, which defaults to 1/3 of physical RAM. Users that wish to exceed the limit must tune vm.max_user_wired. Reviewed by: kib, ngie (mlock() test changes) Tested by: pho (earlier version) MFC after: 45 days Sponsored by: Netflix Differential Revision: https://reviews.freebsd.org/D19908
147 lines
4.6 KiB
Groff
147 lines
4.6 KiB
Groff
.\" $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 above copyright
|
|
.\" notice, this list of conditions and the following disclaimer.
|
|
.\" 2. Redistributions in binary form must reproduce the above copyright
|
|
.\" notice, this list of conditions and the following disclaimer in the
|
|
.\" documentation and/or other materials provided with the distribution.
|
|
.\"
|
|
.\" THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS
|
|
.\" ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
|
|
.\" TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
|
|
.\" PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS
|
|
.\" BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
|
|
.\" CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
|
|
.\" SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
|
|
.\" INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
|
|
.\" CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
|
|
.\" ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
|
|
.\" POSSIBILITY OF SUCH DAMAGE.
|
|
.\"
|
|
.\" $FreeBSD$
|
|
.\"
|
|
.Dd May 13, 2019
|
|
.Dt MLOCKALL 2
|
|
.Os
|
|
.Sh NAME
|
|
.Nm mlockall ,
|
|
.Nm munlockall
|
|
.Nd lock (unlock) the address space of a process
|
|
.Sh LIBRARY
|
|
.Lb libc
|
|
.Sh SYNOPSIS
|
|
.In sys/mman.h
|
|
.Ft int
|
|
.Fn mlockall "int flags"
|
|
.Ft int
|
|
.Fn munlockall "void"
|
|
.Sh 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.
|
|
.Pp
|
|
The following flags affect the behavior of
|
|
.Fn mlockall :
|
|
.Bl -tag -width ".Dv MCL_CURRENT"
|
|
.It Dv MCL_CURRENT
|
|
Lock all pages currently mapped into the process's address space.
|
|
.It Dv 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.
|
|
.El
|
|
.Pp
|
|
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
|
|
.Dq wired pages
|
|
limit
|
|
.Va vm.max_user_wired
|
|
and the per-process
|
|
.Dv RLIMIT_MEMLOCK
|
|
resource limit.
|
|
.Pp
|
|
If
|
|
.Va security.bsd.unprivileged_mlock
|
|
is set to 0 these calls are only available to the super-user.
|
|
If
|
|
.Va vm.old_mlock
|
|
is set to 1 the per-process
|
|
.Dv RLIMIT_MEMLOCK
|
|
resource limit will not be applied for
|
|
.Fn mlockall
|
|
calls.
|
|
.Pp
|
|
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.
|
|
.Sh 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
|
|
.Va errno
|
|
is set to indicate the error.
|
|
.Sh ERRORS
|
|
.Fn mlockall
|
|
will fail if:
|
|
.Bl -tag -width Er
|
|
.It Bq Er EINVAL
|
|
The
|
|
.Fa flags
|
|
argument is zero, or includes unimplemented flags.
|
|
.It Bq Er ENOMEM
|
|
Locking the indicated range would exceed either the system or per-process
|
|
limit for locked memory.
|
|
.It 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.
|
|
.It Bq Er EPERM
|
|
The calling process does not have the appropriate privilege to perform
|
|
the requested operation.
|
|
.El
|
|
.Sh SEE ALSO
|
|
.Xr mincore 2 ,
|
|
.Xr mlock 2 ,
|
|
.Xr mmap 2 ,
|
|
.Xr munmap 2 ,
|
|
.Xr setrlimit 2
|
|
.Sh STANDARDS
|
|
The
|
|
.Fn mlockall
|
|
and
|
|
.Fn munlockall
|
|
functions are believed to conform to
|
|
.St -p1003.1-2001 .
|
|
.Sh HISTORY
|
|
The
|
|
.Fn mlockall
|
|
and
|
|
.Fn munlockall
|
|
functions first appeared in
|
|
.Fx 5.1 .
|
|
.Sh BUGS
|
|
The per-process and system-wide resource limits of locked memory apply
|
|
to the amount of virtual memory locked, not the amount of locked physical
|
|
pages.
|
|
Hence two distinct locked mappings of the same physical page counts as
|
|
2 pages aginst the system limit, and also against the per-process limit
|
|
if both mappings belong to the same physical map.
|