Dear wang, amanda,
How are you measuring CPU usage ? Are you using a tool like 'top' available on Linux ?
My recommendation is that you use the benchmark_app to run some experiments and see how CPU usage is impacted. Keep in mind, your CPU is running lots of other apps also. Fluctuating CPU usage can actually have little to do with your OpenVino application unless you're sure you're narrowing it down using tools like perf (or Vtune).
Hope it helps,