[Pharo-project] Max CPU usage when #drawOn: is overridden

If we override #drawOn: and implement custom logic to draw.. every few milliseconds as it gets called the CPU usage shoots to available max.. Run four instances of the same class that overrides and does some moderately complex draw routine of say : CircleMorph with border set, few lines, color rendering.. I will send in the .st file later .. that can be tested against.. Is this expected or what are the ways to avoid this CPU overhead... NativeBoost animation, far more responsive.. also goes up very similarly. but little more tolerable... VGTigerMorph... more so than FlakesDemo...