i5 6600k 100% CPU usage

Maybe a silly question but is the game using 100% cpu and you have verified by watching the actual game cpu percentage....or is it just the cpu is at full usage??  Reason I ask, is I would get lag spikes back when Dragon Age: Inquisition came out and noticed my cpu was at 100% when it happened, BUT the game was only using 75 to 95% of the draw on a variable scale depending on what was going on in game.  The issue was I had a background program, mine happened to be cleanmem a program designed to clear memory so you didn't have issues(ironically), and it would trigger occasionally  drawing 25% cpu when I was playing the game.  When cleanmem would activate for me the game would freeze or stutter for a few seconds and then would go back to normal.  I ended up using Microsoft Process Explorer and watching the game on one monitor and had the process explorer on the other waiting for a lag spike.  If you use Win10, the upgraded task manager may allow the same thing and for you to find out if the game is the issue, or if something else is hogging cpu time when you need it for the game, which could explain why it only happens sometimes.  Doing a clean boot may also help to figure out if it is a cross program interference....how-to-perform-a-clean-boot-in-windows