2fe8fb192f
There is important information about booting non-ack images in docs/UPDATING. ack/aout-format images can't be built any more, and booting clang/ELF-format ones is a little different. Updating to the new boot monitor is recommended. Changes in this commit: . drop boot monitor -> allowing dropping ack support . facility to copy ELF boot files to /boot so that old boot monitor can still boot fairly easily, see UPDATING . no more ack-format libraries -> single-case libraries . some cleanup of OBJECT_FMT, COMPILER_TYPE, etc cases . drop several ack toolchain commands, but not all support commands (e.g. aal is gone but acksize is not yet). . a few libc files moved to netbsd libc dir . new /bin/date as minix date used code in libc/ . test compile fix . harmonize includes . /usr/lib is no longer special: without ack, /usr/lib plays no kind of special bootstrapping role any more and bootstrapping is done exclusively through packages, so releases depend even less on the state of the machine making them now. . rename nbsd_lib* to lib* . reduce mtree
133 lines
4.4 KiB
Groff
133 lines
4.4 KiB
Groff
.\" $NetBSD: madvise.2,v 1.26 2009/06/03 09:04:18 wiz Exp $
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.\"
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.\" Copyright (c) 1991, 1993
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.\" The Regents of the University of California. All rights reserved.
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.\"
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.\" Redistribution and use in source and binary forms, with or without
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.\" modification, are permitted provided that the following conditions
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.\" are met:
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.\" 1. Redistributions of source code must retain the above copyright
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.\" notice, this list of conditions and the following disclaimer.
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.\" 2. Redistributions in binary form must reproduce the above copyright
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.\" notice, this list of conditions and the following disclaimer in the
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.\" documentation and/or other materials provided with the distribution.
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.\" 3. Neither the name of the University nor the names of its contributors
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.\" may be used to endorse or promote products derived from this software
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.\" without specific prior written permission.
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.\"
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.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
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.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
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.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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.\" SUCH DAMAGE.
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.\"
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.\" @(#)madvise.2 8.1 (Berkeley) 6/9/93
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.\"
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.Dd June 2, 2009
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.Dt MADVISE 2
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.Os
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.Sh NAME
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.Nm madvise
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.Nd give advice about use of memory
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.Sh LIBRARY
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.Lb libc
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.Sh SYNOPSIS
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.In sys/mman.h
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.Ft int
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.Fn madvise "void *addr" "size_t len" "int behav"
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.Ft int
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.Fn posix_madvise "void *addr" "size_t len" "int advice"
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.Sh DESCRIPTION
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The
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.Fn madvise
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system call
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allows a process that has knowledge of its memory behavior
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to describe it to the system.
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The
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.Fn posix_madvise
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interface is identical and is provided for standards conformance.
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.Pp
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The known behaviors are:
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.Bl -tag -width MADV_NORMAL
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.It Dv MADV_NORMAL
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Tells the system to revert to the default paging
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behavior.
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.It Dv MADV_RANDOM
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Is a hint that pages will be accessed randomly, and prefetching
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is likely not advantageous.
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.It Dv MADV_SEQUENTIAL
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Is a hint that pages will be accessed sequentially, from the lower address to
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higher address.
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It might cause the VM system to depress the priority of
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pages immediately preceding a given page when it is faulted in.
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.It Dv MADV_WILLNEED
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Is a hint that pages will be accessed in the near future.
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It might cause the VM system to make pages that are in a given virtual
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address range to temporarily have higher priority, and if they are in
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memory, decrease the likelihood of them being freed.
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It might immediately map the pages that are already in memory into the
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process, thereby eliminating unnecessary overhead of going through
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the entire process of faulting the pages in.
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It might or might not fault pages in from backing store.
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.It Dv MADV_DONTNEED
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Is a hint that pages will not be accessed in the near future.
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It might allow the VM system to decrease the in-memory priority
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of pages in the specified range.
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.It Dv MADV_FREE
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Gives the VM system the freedom to free pages,
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and tells the system that information in the specified page range
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is no longer important.
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.El
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.Pp
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Portable programs that call the
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.Fn posix_madvise
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interface should use the aliases
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.Dv POSIX_MADV_NORMAL , POSIX_MADV_SEQUENTIAL ,
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.Dv POSIX_MADV_RANDOM , POSIX_MADV_WILLNEED ,
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and
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.Dv POSIX_MADV_DONTNEED
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rather than the flags described above.
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.Sh RETURN VALUES
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Upon successful completion,
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a value of 0 is returned.
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Otherwise, a value of \-1 is returned and
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.Va errno
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is set to indicate the error.
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.Sh ERRORS
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.Fn madvise
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will fail if:
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.Bl -tag -width Er
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.It Bq Er EINVAL
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Invalid parameters were provided.
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.El
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.Sh SEE ALSO
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.Xr mincore 2 ,
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.Xr mprotect 2 ,
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.Xr msync 2 ,
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.Xr munmap 2 ,
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.Xr posix_fadvise 2
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.Sh STANDARDS
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The
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.Fn posix_madvise
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system call is expected to conform to the
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.St -p1003.1-2001
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standard.
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.Sh HISTORY
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The
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.Nm madvise
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system call first appeared in
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.Bx 4.4 ,
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but until
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.Nx 1.5
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it did not perform any of the requests on, or change any behavior of the
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address range given.
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The
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.Fn posix_madvise
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was invented in
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.Nx 5.0 .
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