1.\" $OpenBSD: madvise.2,v 1.16 2010/05/19 06:32:43 jmc Exp $ 2.\" $NetBSD: madvise.2,v 1.7 1995/12/27 21:17:02 jtc Exp $ 3.\" 4.\" Copyright (c) 1991, 1993 5.\" The Regents of the University of California. All rights reserved. 6.\" 7.\" Redistribution and use in source and binary forms, with or without 8.\" modification, are permitted provided that the following conditions 9.\" are met: 10.\" 1. Redistributions of source code must retain the above copyright 11.\" notice, this list of conditions and the following disclaimer. 12.\" 2. Redistributions in binary form must reproduce the above copyright 13.\" notice, this list of conditions and the following disclaimer in the 14.\" documentation and/or other materials provided with the distribution. 15.\" 3. Neither the name of the University nor the names of its contributors 16.\" may be used to endorse or promote products derived from this software 17.\" without specific prior written permission. 18.\" 19.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 20.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 21.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 22.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 23.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 24.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 25.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 26.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 27.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 28.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 29.\" SUCH DAMAGE. 30.\" 31.\" @(#)madvise.2 8.1 (Berkeley) 6/9/93 32.\" 33.Dd $Mdocdate: May 19 2010 $ 34.Dt MADVISE 2 35.Os 36.Sh NAME 37.Nm madvise , 38.Nm posix_madvise 39.Nd give advice about use of memory 40.Sh SYNOPSIS 41.Fd #include <sys/mman.h> 42.Ft int 43.Fn madvise "void *addr" "size_t len" "int behav" 44.Ft int 45.Fn posix_madvise "void *addr" "size_t len" "int behav" 46.Sh DESCRIPTION 47The 48.Fn madvise 49system call 50allows a process that has knowledge of its memory behavior 51to describe it to the system. 52The 53.Fn posix_madvise 54interface is identical and is provided for standards conformance. 55.Pp 56The possible behaviors are: 57.Bl -tag -width MADV_SEQUENTIAL 58.It Dv MADV_NORMAL 59No further special treatment needed. 60.It Dv MADV_RANDOM 61Expect random page access patterns. 62.It Dv MADV_SEQUENTIAL 63Expect sequential page references. 64.It Dv MADV_WILLNEED 65The pages will be referenced soon. 66.It Dv MADV_DONTNEED 67The pages will not be referenced soon. 68.It Dv MADV_SPACEAVAIL 69Ensure that resources are reserved. 70.It Dv MADV_FREE 71The pages don't contain any useful data and can be recycled. 72.El 73.Pp 74Portable programs that call the 75.Fn posix_madvise 76interface should use the aliases 77.Dv POSIX_MADV_NORMAL , POSIX_MADV_RANDOM , 78.Dv POSIX_MADV_SEQUENTIAL , POSIX_MADV_WILLNEED , 79and 80.Dv POSIX_MADV_DONTNEED 81rather than the flags described above. 82.Sh RETURN VALUES 83Upon successful completion, 84a value of 0 is returned. 85Otherwise, a value of \-1 is returned and 86.Va errno 87is set to indicate the error. 88.Sh SEE ALSO 89.Xr mincore 2 , 90.Xr minherit 2 , 91.Xr mprotect 2 , 92.Xr msync 2 , 93.Xr munmap 2 94.Sh STANDARDS 95The 96.Fn posix_madvise 97system call is expected to conform to the 98.St -p1003.1-2001 99standard. 100.Sh HISTORY 101The 102.Nm madvise 103function first appeared in 104.Bx 4.4 . 105The 106.Nm posix_madvise 107function first appeared in 108.Ox 4.8 . 109