trusty (3) posix_madvise.3posix.gz

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


       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 .