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PROLOG | NAME | SYNOPSIS | DESCRIPTION | RETURN VALUE | ERRORS | EXAMPLES | APPLICATION USAGE | RATIONALE | FUTURE DIRECTIONS | SEE ALSO | COPYRIGHT |
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POSIX_MADVISE(3P) POSIX Programmer's Manual POSIX_MADVISE(3P)
This manual page is part of the POSIX Programmer's Manual. The
Linux implementation of this interface may differ (consult the
corresponding Linux manual page for details of Linux behavior), or
the interface may not be implemented on Linux.
posix_madvise — memory advisory information and alignment control
(ADVANCED REALTIME)
#include <sys/mman.h>
int posix_madvise(void *addr, size_t len, int advice);
The posix_madvise() function shall advise the implementation on
the expected behavior of the application with respect to the data
in the memory starting at address addr, and continuing for len
bytes. The implementation may use this information to optimize
handling of the specified data. The posix_madvise() function shall
have no effect on the semantics of access to memory in the
specified range, although it may affect the performance of access.
The implementation may require that addr be a multiple of the page
size, which is the value returned by sysconf() when the name value
_SC_PAGESIZE is used.
The advice to be applied to the memory range is specified by the
advice parameter and may be one of the following values:
POSIX_MADV_NORMAL
Specifies that the application has no advice to give on its
behavior with respect to the specified range. It is the
default characteristic if no advice is given for a range of
memory.
POSIX_MADV_SEQUENTIAL
Specifies that the application expects to access the
specified range sequentially from lower addresses to higher
addresses.
POSIX_MADV_RANDOM
Specifies that the application expects to access the
specified range in a random order.
POSIX_MADV_WILLNEED
Specifies that the application expects to access the
specified range in the near future.
POSIX_MADV_DONTNEED
Specifies that the application expects that it will not
access the specified range in the near future.
These values are defined in the <sys/mman.h> header.
Upon successful completion, posix_madvise() shall return zero;
otherwise, an error number shall be returned to indicate the
error.
The posix_madvise() function shall fail if:
EINVAL The value of advice is invalid.
ENOMEM Addresses in the range starting at addr and continuing for
len bytes are partly or completely outside the range
allowed for the address space of the calling process.
The posix_madvise() function may fail if:
EINVAL The value of addr is not a multiple of the value returned
by sysconf() when the name value _SC_PAGESIZE is used.
EINVAL The value of len is zero.
The following sections are informative.
None.
The posix_madvise() function is part of the Advisory Information
option and need not be provided on all implementations.
None.
None.
mmap(3p), posix_fadvise(3p), sysconf(3p)
The Base Definitions volume of POSIX.1‐2017, sys_mman.h(0p)
Portions of this text are reprinted and reproduced in electronic
form from IEEE Std 1003.1-2017, Standard for Information
Technology -- Portable Operating System Interface (POSIX), The
Open Group Base Specifications Issue 7, 2018 Edition, Copyright
(C) 2018 by the Institute of Electrical and Electronics Engineers,
Inc and The Open Group. In the event of any discrepancy between
this version and the original IEEE and The Open Group Standard,
the original IEEE and The Open Group Standard is the referee
document. The original Standard can be obtained online at
http://www.opengroup.org/unix/online.html .
Any typographical or formatting errors that appear in this page
are most likely to have been introduced during the conversion of
the source files to man page format. To report such errors, see
https://www.kernel.org/doc/man-pages/reporting_bugs.html .
IEEE/The Open Group 2017 POSIX_MADVISE(3P)
Pages that refer to this page: fcntl.h(0p), sys_mman.h(0p), posix_fadvise(3p)
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HTML rendering created 2025-09-06 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. |
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