What is the status of POSIX asynchronous I/O (AIO)?

Question

There are pages scattered around the web that describe POSIX AIO facilities in varying amounts of detail. None of them are terribly recent. It\'s not clear what, exactly,

Answer 1

There is aio_write - implemented in glibc; first call of the aio_read or aio_write function spawns a number of user mode threads, aio_write or aio_read post requests to that thread, the thread does pread/pwrite and when it is finished the answer is posted back to the blocked calling thread.

Ther is also 'real' aio - supported by the kernel level (need libaio for that, see the io_submit call http://linux.die.net/man/2/io_submit ); also need O_DIRECT for that (also may not be supported by all file systems, but the major ones do support it)

see here:

http://lse.sourceforge.net/io/aio.html

http://linux.die.net/man/2/io_submit

Difference between POSIX AIO and libaio on Linux?