Provide advisory information about the expected use of memory
Synopsis:
#include <sys/mman.h>
int posix_madvise( void *addr,
size_t len,
int advice );
Arguments:
- addr
- The address of the data the application is providing advice about.
- len
- The length of the data, in bytes.
- advice
- The advice to be applied to the memory range; one of the following:
- POSIX_MADV_DISCARD_NP (QNX Neutrino extension; QNX Neutrino 7.0 or later)
— discard the backing store for lazy private mappings (similar to
madvise(MADV_DONTNEED) in Linux).
The “NP” in the flag name stands for “non-POSIX.”
- POSIX_MADV_DONTNEED — the application expects
that it won't access the data in the near future.
- POSIX_MADV_NORMAL — the application has no
advice to give on its behavior with respect to the specified range.
This is the default characteristic if no advice is given for a range
of memory.
- POSIX_MADV_RANDOM — the application expects
to access the data in a random order.
- POSIX_MADV_SEQUENTIAL — the application expects
to access the data sequentially from lower addresses to higher addresses.
- POSIX_MADV_WILLNEED — the application expects
to access the data in the near future.
Library:
libc
Use the -l c option to
qcc
to link against this library.
This library is usually included automatically.
Description:
The posix_madvise() function advises the memory manager how
the application expects to use the data in the memory starting at address
addr, and continuing for len bytes.
The memory manager may use this information to optimize handling of the data.
Returns:
- EOK
- Success.
- EINVAL
- The value of advice is invalid.
- ENOMEM
- Addresses in the specified range are partly or completely outside
the range allowed for the address space of the calling process.
Classification:
POSIX 1003.1 ADV
| Safety: |
|
|---|
| Cancellation point |
No |
| Interrupt handler |
No |
| Signal handler |
Yes |
| Thread |
Yes |