NetBSD/lib/libc/sys/madvise.2

.\"	$NetBSD: madvise.2,v 1.17 2002/08/11 13:17:35 yamt Exp $
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.\"	@(#)madvise.2	8.1 (Berkeley) 6/9/93
.\"
.Dd August 11, 2002
.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 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 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.