Mathematica GPU occupancy is too high when the current page has high quality images

When Mathematica’s current page contains a high-quality picture, the GPU occupancy rate will increase and the current page delay of Mathematica will increase( the software is slow to respond to my operation.). When I slide the mouse wheel down and turn to the page which does not contain high-quality pictures, and there is no delay of the software, the GPU utilization rate is reduced.

If my current page contains a high-quality graphic like the following code, the GPU utilization rate will become very high:

Eo[x_?NumericQ, z_?NumericQ] = If[15 >= x >= -15 && x <= -z, 1, 0];
DensityPlot[Eo[x, z], {z, -100., 100.}, {x, -100., 100.}, 
 ColorFunction -> "SunsetColors", PlotLegends -> Automatic, 
 Frame -> True, PlotPoints -> 200, Axes -> True, AxesOrigin -> {0, 0},
  AxesLabel -> Automatic]

This problem just appeared today and I have never met this problem before. I want to know if I accidentally set an option wrong? Is there any way to solve this problem?
When Mathematica is used to display high-quality graphics, is it normal to increase the utilization rate of GPU to 70% ?
I try to resetting my Mathematica like this:How do I fix common problems by resetting Mathematica to its default configuration?, but it didn’t work.
By the way, when I reopen a Mathematica project file, the original In[]and Out[] numbers are all gone, it told me In[3] is a previous session, like this:

This my GPU utilization rate screenshots, mathematica doesn’t do anything except show me a picture that I’ve already computed.