Why will “while true” use 100% of CPU resources?

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I ran the following Java code on a Linux server:

while (true) {    int a = 1+2; } 

It caused one CPU core to reach 100% usage. I'm confused about this, because I learnt that CPUs deal with tasks by time splitting, meaning that the CPU will do one task in one time slot (CPU time range scheduler). If there are 10 time slots, the while true task should have at most use 10% CPU usage, because the other 90% would be assigned to other tasks. So why is it 100%?

 


If your CPU usage is not at 100%, then the process can use as much as it wants (up to 100%), until other processes are requesting the use of the resource. The process scheduler attempts to maximize CPU usage, and never leave a process starved of CPU time if there are no other processes that need it.

So your while loop will use 100% of available idle CPU resources, and will only begin to use less when other CPU intensive processes are started up. (if you're using Linux/Unix, you could observe this with top by starting up your while loop, then starting another CPU intensive process and watch the % CPU drop for the process with the loop).

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