posix_madvise(3p) — Linux manual page

POSIX_MADVISE(3P)       POSIX Programmer's Manual      POSIX_MADVISE(3P)

PROLOG

       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.

NAME

       posix_madvise — memory advisory information and alignment control
       (ADVANCED REALTIME)

SYNOPSIS

       #include <sys/mman.h>

       int posix_madvise(void *addr, size_t len, int advice);

DESCRIPTION

       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.

RETURN VALUE

       Upon successful completion, posix_madvise() shall return zero;
       otherwise, an error number shall be returned to indicate the
       error.

ERRORS

       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.

EXAMPLES

       None.

APPLICATION USAGE

       The posix_madvise() function is part of the Advisory Information
       option and need not be provided on all implementations.

RATIONALE

       None.

FUTURE DIRECTIONS

       None.

SEE ALSO

       mmap(3p), posix_fadvise(3p), sysconf(3p)

       The Base Definitions volume of POSIX.1‐2017, sys_mman.h(0p)

COPYRIGHT

       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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