What compute device does the material preview use to render? Recently I have been working on a material library, and when I am working on a complex shader, the preview is updating several times a second. I find that after a while of intense editing and tweaking, my CPU starts to overheat. I am curious if CPU still is used for the material preview even though I have enabled GPU render, or if it is from recalculating the scene data that many times. If it is the latter, are there any solutions?
By using GPU-Z to see gpu load its easy to see that material preview does not use gpu (0% usage). Usage of CPU on the other hand rises when preview updates.

The problem is also how the material preview is coded.


it refreshes with re-scale instead of just computing more samples or only downsizing the preview.
it refreshes not smartly but on every "change". When some value is clicked but not changed, when new node is added but not connected. When you draw line from output and then cancel etc. this could go on and on.


Lot of things blender already has could use more attention from devs..