Averaging isn't ideal, since it hides short-time performance drops. Ideally a value inverse to the duration of the longest frame in the last second or so should

Averaging isn't ideal, since it hides short-time performance drops. Ideally a value inverse to the duration of the longest frame in the last second or so should be displayed as FPS counter. So, if one frame out of 60 was dropped, 30 is displayed instead of 59.