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9bccf70c A |
1 | .\" $NetBSD: madvise.2,v 1.7 1995/12/27 21:17:02 jtc 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. All advertising materials mentioning features or use of this software | |
15 | .\" must display the following acknowledgement: | |
16 | .\" This product includes software developed by the University of | |
17 | .\" California, Berkeley and its contributors. | |
18 | .\" 4. Neither the name of the University nor the names of its contributors | |
19 | .\" may be used to endorse or promote products derived from this software | |
20 | .\" without specific prior written permission. | |
21 | .\" | |
22 | .\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND | |
23 | .\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE | |
24 | .\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE | |
25 | .\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE | |
26 | .\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL | |
27 | .\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS | |
28 | .\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) | |
29 | .\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT | |
30 | .\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY | |
31 | .\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF | |
32 | .\" SUCH DAMAGE. | |
33 | .\" | |
34 | .\" @(#)madvise.2 8.1 (Berkeley) 6/9/93 | |
35 | .\" | |
36 | .Dd June 9, 1993 | |
37 | .Dt MADVISE 2 | |
38 | .Os | |
39 | .Sh NAME | |
2d21ac55 A |
40 | .Nm madvise , |
41 | .Nm posix_madvise | |
9bccf70c A |
42 | .Nd give advice about use of memory |
43 | .Sh SYNOPSIS | |
9bccf70c A |
44 | .Fd #include <sys/mman.h> |
45 | .Ft int | |
2d21ac55 A |
46 | .Fo madvise |
47 | .Fa "void *addr" | |
48 | .Fa "size_t len" | |
49 | .Fa "int advice" | |
50 | .Fc | |
9bccf70c | 51 | .Ft int |
2d21ac55 A |
52 | .Fo posix_madvise |
53 | .Fa "void *addr" | |
54 | .Fa "size_t len" | |
55 | .Fa "int advice" | |
56 | .Fc | |
9bccf70c A |
57 | .Sh DESCRIPTION |
58 | The | |
59 | .Fn madvise | |
2d21ac55 A |
60 | system call allows a process that has knowledge of its memory behavior |
61 | to describe it to the system. | |
62 | The advice passed in may be used by the system | |
63 | to alter its virtual memory paging strategy. | |
64 | This advice may improve application and system performance. | |
65 | The behavior specified in | |
66 | .Fa advice | |
9bccf70c A |
67 | can only be one of the following values: |
68 | .Pp | |
69 | .Bl -tag -width MADV_SEQUENTIAL | |
70 | .It Dv MADV_NORMAL | |
2d21ac55 A |
71 | Indicates that the application has no advice to give on its behavior |
72 | in the specified address range. | |
73 | This is the system default behavior. | |
74 | This is used with | |
9bccf70c A |
75 | .Fn madvise |
76 | system call. | |
77 | .It Dv POSIX_MADV_NORMAL | |
78 | Same as MADV_NORMAL but used with | |
79 | .Fn posix_madvise | |
80 | system call. | |
81 | .It Dv MADV_SEQUENTIAL | |
2d21ac55 A |
82 | Indicates that the application expects to access this address range |
83 | in a sequential manner. | |
84 | This is used with | |
9bccf70c A |
85 | .Fn madvise |
86 | system call. | |
87 | .It Dv POSIX_MADV_SEQUENTIAL | |
88 | Same as MADV_SEQUENTIAL but used with | |
89 | .Fn posix_madvise | |
90 | system call. | |
91 | .It Dv MADV_RANDOM | |
2d21ac55 A |
92 | Indicates that the application expects to access this address range |
93 | in a random manner. | |
94 | This is used with | |
9bccf70c A |
95 | .Fn madvise |
96 | system call. | |
97 | .It Dv POSIX_MADV_RANDOM | |
98 | Same as MADV_RANDOM but used with | |
99 | .Fn posix_madvise | |
100 | system call. | |
101 | .It Dv MADV_WILLNEED | |
2d21ac55 A |
102 | Indicates that the application expects to access this address range soon. |
103 | This is used with | |
9bccf70c A |
104 | .Fn madvise |
105 | system call. | |
106 | .It Dv POSIX_MADV_WILLNEED | |
107 | Same as MADV_WILLNEED but used with | |
108 | .Fn posix_madvise | |
109 | system call. | |
110 | .It Dv MADV_DONTNEED | |
2d21ac55 A |
111 | Indicates that the application is not expecting |
112 | to access this address range soon. | |
113 | This is used with | |
9bccf70c A |
114 | .Fn madvise |
115 | system call. | |
116 | .It Dv POSIX_MADV_DONTNEED | |
117 | Same as MADV_DONTNEED but used with | |
118 | .Fn posix_madvise | |
119 | system call. | |
120 | .It Dv MADV_FREE | |
2d21ac55 A |
121 | Indicates that the application will not need the information contained |
122 | in this address range, so the pages may be reused right away. | |
123 | The address range will remain valid. | |
124 | This is used with | |
9bccf70c A |
125 | .Fn madvise |
126 | system call. | |
127 | .El | |
91447636 | 128 | .Pp |
9bccf70c A |
129 | The |
130 | .Fn posix_madvise | |
131 | behaves same as | |
132 | .Fn madvise | |
133 | except that it uses values with POSIX_ prefix for the | |
2d21ac55 | 134 | .Fa advice |
9bccf70c A |
135 | system call argument. |
136 | .Sh RETURN VALUES | |
137 | Upon successful completion, | |
138 | a value of 0 is returned. | |
139 | Otherwise, a value of -1 is returned and | |
140 | .Va errno | |
141 | is set to indicate the error. | |
142 | .Sh ERRORS | |
143 | .Fn madvise | |
144 | fails if one or more of the following are true: | |
145 | .Bl -tag -width Er | |
2d21ac55 | 146 | .\" ========== |
9bccf70c A |
147 | .It Bq Er EINVAL |
148 | The value of | |
2d21ac55 | 149 | .Fa advice |
9bccf70c | 150 | is incorrect. |
2d21ac55 A |
151 | .\" ========== |
152 | .It Bq Er EINVAL | |
153 | The address range includes unallocated regions. | |
154 | .\" ========== | |
9bccf70c A |
155 | .It Bq Er ENOMEM |
156 | The virtual address range specified by the | |
157 | .Fa addr | |
158 | and | |
159 | .Fa len | |
160 | are outside the range allowed for the address space. | |
9bccf70c | 161 | .El |
2d21ac55 A |
162 | .Sh LEGACY SYNOPSIS |
163 | .Fd #include <sys/types.h> | |
164 | .Fd #include <sys/mman.h> | |
165 | .Pp | |
166 | .Ft int | |
167 | .br | |
168 | .Fo madvise | |
169 | .Fa "caddr_t addr" | |
170 | .Fa "size_t len" | |
171 | .Fa "int advice" | |
172 | .Fc ; | |
173 | .Pp | |
174 | .Ft int | |
175 | .br | |
176 | .Fo posix_madvise | |
177 | .Fa "caddr_t addr" | |
178 | .Fa "size_t len" | |
179 | .Fa "int advice" | |
180 | .Fc ; | |
181 | .Pp | |
182 | The include file | |
183 | .In sys/types.h | |
184 | is necessary. | |
185 | The type of | |
186 | .Fa addr | |
187 | has changed. | |
9bccf70c A |
188 | .Sh SEE ALSO |
189 | .Xr mincore 2 , | |
190 | .Xr minherit 2 , | |
191 | .Xr mprotect 2 , | |
192 | .Xr msync 2 , | |
2d21ac55 A |
193 | .Xr munmap 2 , |
194 | .Xr compat 5 | |
9bccf70c A |
195 | .Sh HISTORY |
196 | The | |
197 | .Nm madvise | |
198 | function first appeared in 4.4BSD. | |
199 | The | |
200 | .Nm posix_madvise | |
2d21ac55 A |
201 | function is part of IEEE 1003.1-2001 |
202 | and was first implemented in Mac OS X 10.2. |