Asynchronous IO (Asynchronous I / O)
asynchronous IO under Linux actually used much, only introduced from kernel version 2.6. Look at its process:
After the user initiates the process of read operations, you can immediately start to do other things. On the other hand, from the kernel's point of view, when it is subjected to a asynchronous read, first of all it will return immediately, so it will not block any user processes. Then, kernel waits for data preparation is complete, and then copy the data to the user memory, when it's all complete, kernel will give the user process to send a signal, telling it read operation is complete.
It is the most efficient model for asynchronous IO