I/O Wait Time: A Guide to Improving Linux Performance
I/O wait is a plaguing issue in Linux. Speaking in layman terms, I/O wait is the time taken by the processor (here, CPU) to complete an input service request. Ideally, our CPU doesn't seem to do any work when it is processing one input request at a time, thus the duration between your input and the output provided by the system can be treated as the I/O wait time.