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 implements demand paging, because file contents are not read from disk directly and initially do not use physical RAM at all. The actual reads from disk are performed in a "lazy" manner, after a specific location is accessed. After the memory is no longer needed, 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).
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