(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  Mem-
       ory 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 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.


              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 original Standard can be obtained online
       at http://www.opengroup.org/unix/online.html .