Mmap

In computing, mmap(2) is a POSIX-compliant Unix system call that maps files or devices into memory. It is a method of memory-mapped file I/O. It naturally implements demand paging, because initially file contents are not entirely read from disk and do not use physical RAM at all. The actual reads from disk are performed in "lazy" manner, after a specific location is accessed. After the memory is not to be used, it is important to munmap(2) the pointers to it. Protection information can be managed using mprotect(2) and special treatment can be enforced using madvise(2).