bionic (3) posix_madvise.3posix.gz

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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(), posix_fadvise(), sysconf()

       The Base Definitions volume of POSIX.1‐2008, <sys_mman.h>


       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 .