CPU usage 100% in I/O operaitions

Question

I have a theoretical question about CPU usage. When the CPU usage goes to 100%, what does it mean ? Does this mean, I have too large data ? Or does this mean I have too large files ? Or too large number of files ? or too much data on JVM ?

This is Java I/O operation done using Multi threaded application.

Answer 1

It means that your application makes more computations than what your CPU can manage such that your CPU is totally overloaded, proportionally it doesn't do much IO compared to computations because IO adds some latency that will consequently reduce the CPU usage, for example an infinite loop with no pause will consume 100 % of the affected CPU .

while(true);

While an infinite loop with a pause will consume much less CPU as we will have less computations to be done per unit of time.

while(true) {
    Thread.sleep(50L);
}