% CPU Time Percentage of time that all processors are executing a non-idle thread. Designed as a primary indicator of processor activity, this counter is calculated by measuring the time that each processor spends executing the thread of the idle process in each sample interval, and subtracting that value from 100%. (Each processor has an idle thread, that consumes cycles when no other threads are ready to run.) It can be viewed as the percentage of the sample interval spent doing useful work. This counter displays the average percentage of busy time observed during the sample interval. It is calculated by monitoring the time, the service was inactive, and then subtracting that value from 100%.