When I use Mathematica 11.1 to make a normal 3D Parametric Plot Mathematica's CPU usage instantly shoots up to 100% on one core as soon as the graphic is rendered. This does not only last until the evaluation has finished, but until I either close the notebook or remove the plot and reevaluate the notebook. Needless to say the entire application slows down, so it's not only the increased battery usage and CPU fan that's annoying.
My system:
Ubuntu 16.04 LTS
Intel i5-7200U
8GB of RAM
Mathematica 11.1
The code I used:
s[a_, z_] := {Cos[a], Sin[a], z}
ParametricPlot3D[s[a, z], {a, 0, 2 Pi}, {z, -5, 5}]
edit: The issue only seems to occur with any shape with two parameters. Plotting just the circumference of a circle works, but filling the circle triggers the high cpu usage.