top) measures the CPU time on waiting for I/O. Many articles say that.
But I am confused that, based on 2 knowledge points:
- if a process uses a system call to read disk, the process is blocked.
- If a process is blocked, it is cannot be scheduled running on CPU.
It seems there no time for CPU waiting on I/O... What happens?
If recommend some books or articles for me to further reading, so much the better.