b6cbf7203b
This patch imports the unmodified current version of NetBSD libc. The NetBSD includes are in /nbsd_include, while the libc code itself is split between lib/nbsd_libc and common/lib/libc.
134 lines
4.4 KiB
Groff
134 lines
4.4 KiB
Groff
.\" $NetBSD: madvise.2,v 1.26 2009/06/03 09:04:18 wiz Exp $
|
|
.\"
|
|
.\" Copyright (c) 1991, 1993
|
|
.\" The Regents of the University of California. All rights reserved.
|
|
.\"
|
|
.\" 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.
|
|
.\" 3. Neither the name of the University nor the names of its contributors
|
|
.\" may be used to endorse or promote products derived from this software
|
|
.\" without specific prior written permission.
|
|
.\"
|
|
.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS 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 REGENTS 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.
|
|
.\"
|
|
.\" @(#)madvise.2 8.1 (Berkeley) 6/9/93
|
|
.\"
|
|
.Dd June 2, 2009
|
|
.Dt MADVISE 2
|
|
.Os
|
|
.Sh NAME
|
|
.Nm madvise
|
|
.Nd give advice about use of memory
|
|
.Sh LIBRARY
|
|
.Lb libc
|
|
.Sh SYNOPSIS
|
|
.In sys/mman.h
|
|
.Ft int
|
|
.Fn madvise "void *addr" "size_t len" "int behav"
|
|
.Ft int
|
|
.Fn posix_madvise "void *addr" "size_t len" "int advice"
|
|
.Sh DESCRIPTION
|
|
The
|
|
.Fn madvise
|
|
system call
|
|
allows a process that has knowledge of its memory behavior
|
|
to describe it to the system.
|
|
The
|
|
.Fn posix_madvise
|
|
interface is identical and is provided for standards conformance.
|
|
.Pp
|
|
The known behaviors are:
|
|
.Bl -tag -width MADV_NORMAL
|
|
.It Dv MADV_NORMAL
|
|
Tells the system to revert to the default paging
|
|
behavior.
|
|
.It Dv MADV_RANDOM
|
|
Is a hint that pages will be accessed randomly, and prefetching
|
|
is likely not advantageous.
|
|
.It Dv MADV_SEQUENTIAL
|
|
Is a hint that pages will be accessed sequentially, from the lower address to
|
|
higher address.
|
|
It might cause the VM system to depress the priority of
|
|
pages immediately preceding a given page when it is faulted in.
|
|
.It Dv MADV_WILLNEED
|
|
Is a hint that pages will be accessed in the near future.
|
|
It might cause the VM system to make pages that are in a given virtual
|
|
address range to temporarily have higher priority, and if they are in
|
|
memory, decrease the likelihood of them being freed.
|
|
It might immediately map the pages that are already in memory into the
|
|
process, thereby eliminating unnecessary overhead of going through
|
|
the entire process of faulting the pages in.
|
|
It might or might not fault pages in from backing store.
|
|
.It Dv MADV_DONTNEED
|
|
Is a hint that pages will not be accessed in the near future.
|
|
It might allow the VM system to decrease the in-memory priority
|
|
of pages in the specified range.
|
|
.It Dv MADV_FREE
|
|
Gives the VM system the freedom to free pages,
|
|
and tells the system that information in the specified page range
|
|
is no longer important.
|
|
.El
|
|
.Pp
|
|
Portable programs that call the
|
|
.Fn posix_madvise
|
|
interface should use the aliases
|
|
.Dv POSIX_MADV_NORMAL , POSIX_MADV_SEQUENTIAL ,
|
|
.Dv POSIX_MADV_RANDOM , POSIX_MADV_WILLNEED ,
|
|
and
|
|
.Dv POSIX_MADV_DONTNEED
|
|
rather than the flags described above.
|
|
.Sh RETURN VALUES
|
|
Upon successful completion,
|
|
a value of 0 is returned.
|
|
Otherwise, a value of \-1 is returned and
|
|
.Va errno
|
|
is set to indicate the error.
|
|
.Sh ERRORS
|
|
.Fn madvise
|
|
will fail if:
|
|
.Bl -tag -width Er
|
|
.It Bq Er EINVAL
|
|
Invalid parameters were provided.
|
|
.El
|
|
.Sh SEE ALSO
|
|
.Xr mincore 2 ,
|
|
.Xr mprotect 2 ,
|
|
.Xr msync 2 ,
|
|
.Xr munmap 2 ,
|
|
.Xr posix_fadvise 2
|
|
.Sh STANDARDS
|
|
The
|
|
.Fn posix_madvise
|
|
system call is expected to conform to the
|
|
.St -p1003.1-2001
|
|
standard.
|
|
.Sh HISTORY
|
|
The
|
|
.Nm madvise
|
|
system call first appeared in
|
|
.Bx 4.4 ,
|
|
but until
|
|
.Nx 1.5
|
|
it did not perform any of the requests on, or change any behavior of the
|
|
address range given.
|
|
The
|
|
.Fn posix_madvise
|
|
was invented in
|
|
.Nx 5.0 .
|