posix_madvise - memory advisory information
#include <sys/mman.h> int posix_madvise(void *addr, size_t len, int advice);
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:
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.
Specifies that the application expects to access the specified range sequentially from lower addresses to higher addresses.
Specifies that the application expects to access the specified range in a random order.
Specifies that the application expects to access the specified range in the near future.
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
Upon successful completion, posix_madvise() returns zero. Otherwise, an error number is returned to indicate the error.
The posix_madvise() function will fail if:
The value of advice is invalid.
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:
The value of len is zero.
See attributes(7) for descriptions of the following attributes: