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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21 The posix_madvise() function shall advise the implementation on the
22 expected behavior of the application with respect to the data in the
23 memory starting at address addr, and continuing for len bytes. The
24 implementation may use this information to optimize handling of the
25 specified data. The posix_madvise() function shall have no effect on
26 the semantics of access to memory in the specified range, although it
27 may affect the performance of access.
28 The implementation may require that addr be a multiple of the page
30 size, which is the value returned by sysconf() when the name value
31 _SC_PAGESIZE is used.
32 The advice to be applied to the memory range is specified by the advice
34 parameter and may be one of the following values:
35 POSIX_MADV_NORMAL
37 Specifies that the application has no advice to give on its
38 behavior with respect to the specified range. It is the default
39 characteristic if no advice is given for a range of memory.
40 POSIX_MADV_SEQUENTIAL
42 Specifies that the application expects to access the specified
43 range sequentially from lower addresses to higher addresses.
44 POSIX_MADV_RANDOM
46 Specifies that the application expects to access the specified
47 range in a random order.
48 POSIX_MADV_WILLNEED
50 Specifies that the application expects to access the specified
51 range in the near future.
52 POSIX_MADV_DONTNEED
54 Specifies that the application expects that it will not access
55 the specified range in the near future.
56 These values are defined in the <sys/mman.h> header.
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60 Upon successful completion, posix_madvise() shall return zero; other‐
61 wise, an error number shall be returned to indicate the error.
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64 The posix_madvise() function shall fail if:
65 EINVAL The value of advice is invalid.
67 ENOMEM Addresses in the range starting at addr and continuing for len
69 bytes are partly or completely outside the range allowed for the
70 address space of the calling process.
71 The posix_madvise() function may fail if:
73 EINVAL The value of addr is not a multiple of the value returned by
75 sysconf() when the name value _SC_PAGESIZE is used.
76 EINVAL The value of len is zero.
78 The following sections are informative.
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82 None.
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85 The posix_madvise() function is part of the Advisory Information option
86 and need not be provided on all implementations.
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89 None.
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92 None.
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95 mmap(), posix_fadvise(), sysconf()
96 The Base Definitions volume of POSIX.1‐2017, <sys_mman.h>
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100 Portions of this text are reprinted and reproduced in electronic form
101 from IEEE Std 1003.1-2017, Standard for Information Technology -- Por‐
102 table Operating System Interface (POSIX), The Open Group Base Specifi‐
103 cations Issue 7, 2018 Edition, Copyright (C) 2018 by the Institute of
104 Electrical and Electronics Engineers, Inc and The Open Group. In the
105 event of any discrepancy between this version and the original IEEE and
106 The Open Group Standard, the original IEEE and The Open Group Standard
107 is the referee document. The original Standard can be obtained online
108 at http://www.opengroup.org/unix/online.html .
109 Any typographical or formatting errors that appear in this page are
111 most likely to have been introduced during the conversion of the source
112 files to man page format. To report such errors, see https://www.ker‐
113 nel.org/doc/man-pages/reporting_bugs.html .
114IEEE/The Open Group 2017 POSIX_MADVISE(3P)