Asynchronous I/O (AIO)

Without AIO, when an application needs to get data from a hardware device or a network connection, it can either poll the connection until the data is available or spawn a thread for the connection that waits for the data. Neither of these techniques is efficient.

Asynchronous I/O allows the kernel to notify an application when it has data ready to be read. This feature is most useful to large servers but can provide moderate performance gains in almost any application.