Vectored I/O & Memory-Mapping

This topic covers two aspects of Advanced File I/O: (1) Scatter/gather I/O [= Vectored I/O] and (2) Memory-mapped I/O.

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Scatter/Gather I/O, also known as Vectored I/O, is a method in which a single syscall reads or writes a vector (= array) of buffers from a single data file stream.

The advantages of Scatter/Gather I/O over linear I/O (= regular I/O as we've covered so far) are:

• More natural coding pattern: intuitive for naturally segmented data, e.g., multiple lines or strings of text.
• Efficiency: a single vectored I/O operation is used instead of multiple linear I/O calls.
• Performance: the OS can optimize the I/O operations done via Scatter/Gather I/O, making this method faster than multiple linear I/O calls.
• Locked: there is no risk of interleaving (= messing up) I/O from another process or thread.