1.\" $NetBSD: madvise.2,v 1.23 2006/10/13 20:52:08 wiz Exp $ 2.\" 3.\" Copyright (c) 1991, 1993 4.\" The Regents of the University of California. All rights reserved. 5.\" 6.\" Redistribution and use in source and binary forms, with or without 7.\" modification, are permitted provided that the following conditions 8.\" are met: 9.\" 1. Redistributions of source code must retain the above copyright 10.\" notice, this list of conditions and the following disclaimer. 11.\" 2. Redistributions in binary form must reproduce the above copyright 12.\" notice, this list of conditions and the following disclaimer in the 13.\" documentation and/or other materials provided with the distribution. 14.\" 3. Neither the name of the University nor the names of its contributors 15.\" may be used to endorse or promote products derived from this software 16.\" without specific prior written permission. 17.\" 18.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 19.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 20.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 21.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 22.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 23.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 24.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 25.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 26.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 27.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 28.\" SUCH DAMAGE. 29.\" 30.\" @(#)madvise.2 8.1 (Berkeley) 6/9/93 31.\" 32.Dd October 7, 2006 33.Dt MADVISE 2 34.Os 35.Sh NAME 36.Nm madvise 37.Nd give advice about use of memory 38.Sh LIBRARY 39.Lb libc 40.Sh SYNOPSIS 41.In sys/mman.h 42.Ft int 43.Fn madvise "void *addr" "size_t len" "int behav" 44.Sh DESCRIPTION 45The 46.Fn madvise 47system call 48allows a process that has knowledge of its memory behavior 49to describe it to the system. 50The known behaviors are given in 51.Pa \*[Lt]sys/mman.h\*[Gt] : 52.Bd -literal 53#define MADV_NORMAL 0 /* no further special treatment */ 54#define MADV_RANDOM 1 /* expect random page references */ 55#define MADV_SEQUENTIAL 2 /* expect sequential references */ 56#define MADV_WILLNEED 3 /* will need these pages */ 57#define MADV_DONTNEED 4 /* don't need these pages */ 58#define MADV_SPACEAVAIL 5 /* ensure that resources are reserved */ 59#define MADV_FREE 6 /* pages are empty, free them */ 60.Ed 61.Sh RETURN VALUES 62Upon successful completion, 63a value of 0 is returned. 64Otherwise, a value of \-1 is returned and 65.Va errno 66is set to indicate the error. 67.Sh ERRORS 68.Fn madvise 69will fail if: 70.Bl -tag -width Er 71.It Bq Er EINVAL 72Invalid parameters were provided. 73.El 74.Sh SEE ALSO 75.Xr mincore 2 , 76.Xr mprotect 2 , 77.Xr msync 2 , 78.Xr munmap 2 79.Sh HISTORY 80The 81.Nm madvise 82system call first appeared in 83.Bx 4.4 , 84but until 85.Nx 1.5 86it did not perform any of the requests on, or change any behavior of the 87address range given. 88