POSIX_MADVISE(3C) Standard C Library Functions POSIX_MADVISE(3C)

NAME

posix_madvise - memory advisory information

SYNOPSIS

#include <sys/mman.h>

int posix_madvise(void *addr, size_t len, int advice);

DESCRIPTION

The posix_madvise() function advises the system 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 system may use this
information to optimize handling of the specified data. The
posix_madvise() function has no effect on the semantics of access to
memory in the specified range, although it may affect the performance of
access.


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 <sys/mman.h>

RETURN VALUES

Upon successful completion, posix_madvise() returns zero. Otherwise, an
error number is returned to indicate the error.

ERRORS

The posix_madvise() function will 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 len is zero.

ATTRIBUTES

See attributes(7) for descriptions of the following attributes:


+--------------------+-------------------+
| ATTRIBUTE TYPE | ATTRIBUTE VALUE |
+--------------------+-------------------+
|Interface Stability | Committed |
+--------------------+-------------------+
|MT-Level | MT-Safe |
+--------------------+-------------------+
|Standard | See standards(7). |
+--------------------+-------------------+

SEE ALSO

mmap(2), madvise(3C), posix_madvise(3C), attributes(7), standards(7)


July 14, 2008 POSIX_MADVISE(3C)