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

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 need only be supported if either the Memory Mapped Files or
       the Shared Memory Objects options are supported.

       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 con-
       tinuing 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()	,   posix_fadvise()   ,   sysconf()   ,   the	Base   Definitions   volume    of
       IEEE Std 1003.1-2001, <sys/mman.h>

COPYRIGHT
       Portions  of  this  text  are  reprinted  and  reproduced in electronic form from IEEE Std
       1003.1, 2003 Edition, Standard for Information Technology  --  Portable	Operating  System
       Interface  (POSIX), The Open Group Base Specifications Issue 6, Copyright (C) 2001-2003 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 orig-
       inal Standard can be obtained online at http://www.opengroup.org/unix/online.html .

IEEE/The Open Group			       2003				 POSIX_MADVISE(P)
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