mprotect() can be used to change the protection setings (NONE, READ, WRITE, EXEC) for a specific region in the mapping. The address passed in must be on page boundary.
The function of msync is equivalent to fsync in normal IO. The data in the file or the specified region of the file associated with a mapping is written back to the disk. The mode of flushing is controlled by a flag - MS_SYNC, MS_ASYNC and MS_INVALIDATE. The last option invalidates all copies of the file mapping and future access will see the current file content on disk.
madvice() allows caller to hint kernel on the intended usage of the file memory mapping so that kernel can make intelligent optimization of the operation:
MADV_NORMAL - perform a moderate amount of read ahead
MADV_RANDOM - disable read ahead and read a minimal amount of data for each physcial read
MADV_SEQUENTIAL - perform read ahead aggressively
MADV_WILLNEED - initiate read ahead
MADV_DONTNEED - free the pages and discard all dirty ones. Subsequent access to the pages will caused the page to be read in from backing store or zero-filled page (anonymous) again.
MADV_DONTFORK - do not copy the pages across fork. Used mainly for managing DMA pages
for example, madvise(addr, len, MADV_SEQUENTIAL) informs the kernel that the program intend to access the memory regional sequentially.
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