NetBSD/lib/libc/sys/madvise.2

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.\" $NetBSD: madvise.2,v 1.16 2002/02/08 01:28:19 ross Exp $
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.\" Copyright (c) 1991, 1993
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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 LIBRARY
.Lb libc
.Sh SYNOPSIS
.Fd #include \*[Lt]sys/mman.h\*[Gt]
.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 known behaviors are given in
.Pa \*[Lt]sys/mman.h\*[Gt] :
.Bd -literal
#define MADV_NORMAL 0 /* no further special treatment */
#define MADV_RANDOM 1 /* expect random page references */
#define MADV_SEQUENTIAL 2 /* expect sequential references */
#define MADV_WILLNEED 3 /* will need these pages */
#define MADV_DONTNEED 4 /* don't need these pages */
#define MADV_SPACEAVAIL 5 /* ensure that resources are reserved */
#define MADV_FREE 6 /* pages are empty, free them */
.Ed
.Sh SEE ALSO
.Xr mincore 2 ,
.Xr mprotect 2 ,
.Xr msync 2 ,
.Xr munmap 2
.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.