|WP1 - RTOS State of the Art Analysis: Deliverable D1.1 - RTOS Analysis|
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Asynchronous I/O (AIO) is the POSIX interface to provide high efficiency asynchronous I/O access. The standard way to access I/O devices (files, drivers, sockets, fifos, etc.) defined by UNIX the read() write() blocking sequence, where a next file access is performed only when the previous request has been completed. AIO mechanism provides the ability to overlap application processing and I/O operations initiated by the application.
A process can start one or more IO requests to a single file or multiples files and continue its execution. Also, a single system call can start a sequence of I/O operation on one or several files, which reduces the overhead due to context switches.
There are two implementations available in Linux: the one provided at the library level by using non-aio system calls (included in the glibc/librt since version 2.1); and the kernel implementation first developed by SGI™ called KAIO (till linux kernel 2.4.0), and now the Linux-AIO which provides this functionality to newer kernels.