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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13 posix_madvise — memory advisory information and alignment control
14 (ADVANCED REALTIME)
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17 #include <sys/mman.h>
18 int posix_madvise(void *addr, size_t len, int advice);
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22 The posix_madvise() function shall advise the implementation on the
23 expected behavior of the application with respect to the data in the
24 memory starting at address addr, and continuing for len bytes. The
25 implementation may use this information to optimize handling of the
26 specified data. The posix_madvise() function shall have no effect on
27 the semantics of access to memory in the specified range, although it
28 may affect the performance of access.
29 The implementation may require that addr be a multiple of the page
31 size, which is the value returned by sysconf() when the name value
32 _SC_PAGESIZE is used.
33 The advice to be applied to the memory range is specified by the advice
35 parameter and may be one of the following values:
36 POSIX_MADV_NORMAL
38 Specifies that the application has no advice to give on its
39 behavior with respect to the specified range. It is the default
40 characteristic if no advice is given for a range of memory.
41 POSIX_MADV_SEQUENTIAL
43 Specifies that the application expects to access the specified
44 range sequentially from lower addresses to higher addresses.
45 POSIX_MADV_RANDOM
47 Specifies that the application expects to access the specified
48 range in a random order.
49 POSIX_MADV_WILLNEED
51 Specifies that the application expects to access the specified
52 range in the near future.
53 POSIX_MADV_DONTNEED
55 Specifies that the application expects that it will not access
56 the specified range in the near future.
57 These values are defined in the <sys/mman.h> header.
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61 Upon successful completion, posix_madvise() shall return zero; other‐
62 wise, an error number shall be returned to indicate the error.
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65 The posix_madvise() function shall fail if:
66 EINVAL The value of advice is invalid.
68 ENOMEM Addresses in the range starting at addr and continuing for len
70 bytes are partly or completely outside the range allowed for the
71 address space of the calling process.
72 The posix_madvise() function may fail if:
74 EINVAL The value of addr is not a multiple of the value returned by
76 sysconf() when the name value _SC_PAGESIZE is used.
77 EINVAL The value of len is zero.
79 The following sections are informative.
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83 None.
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86 The posix_madvise() function is part of the Advisory Information option
87 and need not be provided on all implementations.
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90 None.
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93 None.
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96 mmap(), posix_fadvise(), sysconf()
97 The Base Definitions volume of POSIX.1‐2008, <sys_mman.h>
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101 Portions of this text are reprinted and reproduced in electronic form
102 from IEEE Std 1003.1, 2013 Edition, Standard for Information Technology
103 -- Portable Operating System Interface (POSIX), The Open Group Base
104 Specifications Issue 7, Copyright (C) 2013 by the Institute of Electri‐
105 cal and Electronics Engineers, Inc and The Open Group. (This is
106 POSIX.1-2008 with the 2013 Technical Corrigendum 1 applied.) In the
107 event of any discrepancy between this version and the original IEEE and
108 The Open Group Standard, the original IEEE and The Open Group Standard
109 is the referee document. The original Standard can be obtained online
110 at http://www.unix.org/online.html .
111 Any typographical or formatting errors that appear in this page are
113 most likely to have been introduced during the conversion of the source
114 files to man page format. To report such errors, see https://www.ker‐
115 nel.org/doc/man-pages/reporting_bugs.html .
116IEEE/The Open Group 2013 POSIX_MADVISE(3P)