Originální popis anglicky:
posix_madvise - memory advisory information and alignment control (
ADVANCED
REALTIME)
Návod, kniha: POSIX Programmer's Manual
#include <sys/mman.h>
int posix_madvise(void *
addr, size_t
len , int advice);
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.
Upon successful completion,
posix_madvise() shall return zero; otherwise,
an error number shall be returned to indicate the error.
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.
None.
The
posix_madvise() function is part of the Advisory Information option
and need not be provided on all implementations.
None.
None.
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
.
