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.\"	$NetBSD: madvise.2,v 1.7 1995/12/27 21:17:02 jtc Exp $
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.\"	@(#)madvise.2	8.1 (Berkeley) 6/9/93
.\"
.Dd June 9, 1993
.Dt MADVISE 2
.Os
.Sh NAME
.Nm madvise
.Nd give advice about use of memory
.Sh SYNOPSIS
.Fd #include <sys/types.h>
.Fd #include <sys/mman.h>
.Ft int
.Fn madvise "void *addr" "size_t len" "int behav"
.Sh DESCRIPTION
The
.Fn madvise
system call
allows a process that has knowledge of its memory behavior
to describe it to the system.
The possible behaviors are:
.Bl -tag -width MADV_SEQUENTIAL
.It Dv MADV_NORMAL
No further special treatment needed.
.It Dv MADV_RANDOM
Expect random page access patterns.
.It Dv MADV_SEQUENTIAL
Expect sequential page references.
.It Dv MADV_WILLNEED
The pages will be referenced soon.
.It Dv MADV_DONTNEED
The pages will not be referenced soon.
.It Dv MADV_SPACEAVAIL
Insure that resources are reserved.
.It Dv MADV_FREE
The pages don't contain any useful data and can be recycled.
.El
.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 SEE ALSO
.Xr mincore 2 ,
.Xr minherit 2 ,
.Xr mprotect 2 ,
.Xr msync 2 ,
.Xr munmap 2
.Sh HISTORY
The
.Nm madvise
function first appeared in
.Bx 4.4 .