1POSIX_MADVISE(3P) POSIX Programmer's Manual POSIX_MADVISE(3P)
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6 This manual page is part of the POSIX Programmer's Manual. The Linux
7 implementation of this interface may differ (consult the corresponding
8 Linux manual page for details of Linux behavior), or the interface may
9 not be implemented on Linux.
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12 posix_madvise - memory advisory information and alignment control
13 (ADVANCED REALTIME)
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16 #include <sys/mman.h>
17 int posix_madvise(void *addr, size_t len, int advice);
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22 The posix_madvise() function need only be supported if either the Mem‐
23 ory Mapped Files or the Shared Memory Objects options are supported.
24 The posix_madvise() function shall advise the implementation on the
26 expected behavior of the application with respect to the data in the
27 memory starting at address addr, and continuing for len bytes. The
28 implementation may use this information to optimize handling of the
29 specified data. The posix_madvise() function shall have no effect on
30 the semantics of access to memory in the specified range, although it
31 may affect the performance of access.
32 The implementation may require that addr be a multiple of the page
34 size, which is the value returned by sysconf() when the name value
35 _SC_PAGESIZE is used.
36 The advice to be applied to the memory range is specified by the advice
38 parameter and may be one of the following values:
39 POSIX_MADV_NORMAL
41 Specifies that the application has no advice to give on its
43 behavior with respect to the specified range. It is the default
44 characteristic if no advice is given for a range of memory.
45 POSIX_MADV_SEQUENTIAL
47 Specifies that the application expects to access the specified
49 range sequentially from lower addresses to higher addresses.
50 POSIX_MADV_RANDOM
52 Specifies that the application expects to access the specified
54 range in a random order.
55 POSIX_MADV_WILLNEED
57 Specifies that the application expects to access the specified
59 range in the near future.
60 POSIX_MADV_DONTNEED
62 Specifies that the application expects that it will not access
64 the specified range in the near future.
65 These values are defined in the <sys/mman.h> header.
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70 Upon successful completion, posix_madvise() shall return zero; other‐
71 wise, an error number shall be returned to indicate the error.
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74 The posix_madvise() function shall fail if:
75 EINVAL The value of advice is invalid.
77 ENOMEM Addresses in the range starting at addr and continuing for len
79 bytes are partly or completely outside the range allowed for the
80 address space of the calling process.
81 The posix_madvise() function may fail if:
84 EINVAL The value of addr is not a multiple of the value returned by
86 sysconf() when the name value _SC_PAGESIZE is used.
87 EINVAL The value of len is zero.
89 The following sections are informative.
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94 None.
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97 The posix_madvise() function is part of the Advisory Information option
98 and need not be provided on all implementations.
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101 None.
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104 None.
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107 mmap(), posix_fadvise(), sysconf(), the Base Definitions volume of
108 IEEE Std 1003.1-2001, <sys/mman.h>
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111 Portions of this text are reprinted and reproduced in electronic form
112 from IEEE Std 1003.1, 2003 Edition, Standard for Information Technology
113 -- Portable Operating System Interface (POSIX), The Open Group Base
114 Specifications Issue 6, Copyright (C) 2001-2003 by the Institute of
115 Electrical and Electronics Engineers, Inc and The Open Group. In the
116 event of any discrepancy between this version and the original IEEE and
117 The Open Group Standard, the original IEEE and The Open Group Standard
118 is the referee document. The original Standard can be obtained online
119 at http://www.opengroup.org/unix/online.html .
120IEEE/The Open Group 2003 POSIX_MADVISE(3P)