225 lines
6.1 KiB
Groff
225 lines
6.1 KiB
Groff
.\" $NetBSD: madvise.2,v 1.7 1995/12/27 21:17:02 jtc 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. All advertising materials mentioning features or use of this software
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.\" must display the following acknowledgement:
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.\" This product includes software developed by the University of
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.\" California, Berkeley and its contributors.
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.\" 4. 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 9, 1993
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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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.Nm posix_madvise
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.Nd give advice about use of memory
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.Sh SYNOPSIS
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.Fd #include <sys/mman.h>
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.Ft int
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.Fo madvise
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.Fa "void *addr"
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.Fa "size_t len"
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.Fa "int advice"
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.Fc
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.Ft int
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.Fo posix_madvise
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.Fa "void *addr"
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.Fa "size_t len"
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.Fa "int advice"
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.Fc
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.Sh DESCRIPTION
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The
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.Fn madvise
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system call 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 advice passed in may be used by the system
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to alter its virtual memory paging strategy.
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This advice may improve application and system performance.
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The behavior specified in
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.Fa advice
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can only be one of the following values:
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.Pp
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.Bl -tag -width MADV_SEQUENTIAL
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.It Dv MADV_NORMAL
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Indicates that the application has no advice to give on its behavior
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in the specified address range.
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This is the system default behavior.
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This is used with
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.Fn madvise
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system call.
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.It Dv POSIX_MADV_NORMAL
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Same as MADV_NORMAL but used with
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.Fn posix_madvise
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system call.
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.It Dv MADV_SEQUENTIAL
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Indicates that the application expects to access this address range
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in a sequential manner.
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This is used with
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.Fn madvise
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system call.
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.It Dv POSIX_MADV_SEQUENTIAL
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Same as MADV_SEQUENTIAL but used with
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.Fn posix_madvise
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system call.
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.It Dv MADV_RANDOM
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Indicates that the application expects to access this address range
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in a random manner.
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This is used with
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.Fn madvise
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system call.
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.It Dv POSIX_MADV_RANDOM
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Same as MADV_RANDOM but used with
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.Fn posix_madvise
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system call.
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.It Dv MADV_WILLNEED
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Indicates that the application expects to access this address range soon.
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This is used with
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.Fn madvise
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system call.
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.It Dv POSIX_MADV_WILLNEED
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Same as MADV_WILLNEED but used with
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.Fn posix_madvise
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system call.
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.It Dv MADV_DONTNEED
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Indicates that the application is not expecting
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to access this address range soon.
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This is used with
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.Fn madvise
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system call.
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.It Dv POSIX_MADV_DONTNEED
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Same as MADV_DONTNEED but used with
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.Fn posix_madvise
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system call.
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.It Dv MADV_FREE
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Indicates that the application will not need the information contained
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in this address range, so the pages may be reused right away.
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The address range will remain valid.
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This is used with
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.Fn madvise
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system call.
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.It Dv MADV_ZERO_WIRED_PAGES
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Indicates that the application would like the wired pages in this address
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range to be zeroed out if the address range is deallocated without first
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unwiring the pages (i.e. a munmap(2) without a preceding munlock(2) or the application
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quits).
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This is used with
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.Fn madvise
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system call.
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.It Dv MADV_ZERO
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Indicates that the application would like this address range effectively
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zeroed without causing unnecessary memory accesses. This could return ENOTSUP
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in some situations, in which case the caller should fall back to zeroing the
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range themselves.
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This is used with
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.Fn madvise
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system call.
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.El
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.Pp
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The
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.Fn posix_madvise
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behaves same as
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.Fn madvise
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except that it uses values with POSIX_ prefix for the
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.Fa advice
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system call argument.
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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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fails if one or more of the following are true:
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.Bl -tag -width Er
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.\" ==========
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.It Bq Er EINVAL
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The value of
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.Fa advice
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is incorrect.
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.\" ==========
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.It Bq Er EINVAL
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The address range includes unallocated regions.
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.\" ==========
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.It Bq Er ENOMEM
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The virtual address range specified by the
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.Fa addr
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and
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.Fa len
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are outside the range allowed for the address space.
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.\" ==========
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.It Bq Er EPERM
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The operation isn't allowed on a part (or whole) of the address range due to
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restrictions.
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.\" ==========
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.It Bq Er ENOTSUP
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The operation is not supported.
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.El
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.Sh LEGACY SYNOPSIS
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.Fd #include <sys/types.h>
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.Fd #include <sys/mman.h>
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.Pp
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.Ft int
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.br
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.Fo madvise
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.Fa "caddr_t addr"
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.Fa "size_t len"
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.Fa "int advice"
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.Fc ;
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.Pp
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.Ft int
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.br
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.Fo posix_madvise
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.Fa "caddr_t addr"
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.Fa "size_t len"
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.Fa "int advice"
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.Fc ;
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.Pp
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The include file
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.In sys/types.h
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is necessary.
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The type of
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.Fa addr
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has changed.
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.Sh SEE ALSO
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.Xr mincore 2 ,
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.Xr minherit 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 compat 5
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.Sh HISTORY
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The
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.Nm madvise
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function first appeared in 4.4BSD.
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The
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.Nm posix_madvise
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function is part of IEEE 1003.1-2001
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and was first implemented in Mac OS X 10.2.
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