Help for AIO

[ftp21]

Hello,
Where i can found some info about AIO?

I need to know how work and what is this feature in LS.

Today, after upgrade to 4.1.13 i see these messages in error_log

2012-07-11 10:42:32.223 [INFO] [:53184-0] Pending AIO operation, recycle later...
2012-07-11 10:42:32.550 [INFO] [:53184-0] Pending AIO finished, recycle connection.

I use LS v4.1.13.

Waiting for your reply.