madvise - give advice about use of memory
#include <sys/mman.h>
int madvise(void *start, size_t length, int advice );
The madvise(2) system call advises the kernel about how to handle paging input/output in the address range beginning at address start and with size length bytes. It allows an application to tell the kernel how it expects to use some mapped or shared memory areas, so that the kernel can choose appropriate read-ahead and caching techniques. This call does not influence the semantics of the application, but may influence its performance. The kernel is free to ignore the advice.
The advice is indicated in the advice parameter which can be
On success madvise(2) returns zero. On error, it returns -1 and errno is set appropiately.
The current Linux implementation (2.4.0) views this system call more as a command than as advice and hence may return an error when it cannot do what it usually would do in response to this advice. (See the ERRORS description above.) This is nonstandard behaviour.
The Linux implementation requires that the address start be page-aligned, and allows length to be zero. If there are some parts of the specified address range that are not mapped, the Linux version of madvise(2) ignores them and applies the call to the rest (but returns ENOMEM from the system call, as it should).
The madvise function first appeared in 4.4BSD.
POSIX.1b (POSIX.4). The Austin draft describes posix_madvise with constants POSIX_MADV_NORMAL, etc., with a behaviour close to that described here. There is a similar posix_fadvise for file access.
getrlimit(2), mmap(2), mincore(2), mprotect(2), msync(2), munmap(2)
One page links to madvise(2):