Until now, we have seen how I/O works from a hardware and software perspective. We mentioned that it is possible to have our process working while waiting for the I/O, but how do we do it?
The kernel has some things to help us with this. In the case of Linux, it has the epoll() system call, which lets the kernel know that our code wants to receive some information from an I/O interface, but that it doesn't need to lock itself until the information is available. The kernel will know what callback to run when the information is ready, and meanwhile, our program can do a lot of computations.
This is very useful, for example, if we are processing some data and we know that in the future ...
