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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.1‐2008, sys_mman.h(0p)
Portions of this text are reprinted and reproduced in electronic form
from IEEE Std 1003.1, 2013 Edition, Standard for Information
Technology -- Portable Operating System Interface (POSIX), The Open
Group Base Specifications Issue 7, Copyright (C) 2013 by the
Institute of Electrical and Electronics Engineers, Inc and The Open
Group. (This is POSIX.1-2008 with the 2013 Technical Corrigendum 1
applied.) 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.unix.org/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 2013 POSIX_MADVISE(3P)
Pages that refer to this page: fcntl.h(0p), sys_mman.h(0p), posix_fadvise(3p)