[Bf-cycles] GPU Workload with finished preview

[Constantin Rahn]

Hey Brecht,

some time ago we have had a small conversation on IRC about my 
observation, that my GPU fan is running very high with the finished 
preview (GPU-rendering). Closing the cycles preview (switch to material 
or shaded preview) will slow down the GPU fan a few seconds later.

With the latest r55891 the effect is still there.
Win7 64
gforce GTX 680

Based only on the sound of the fan I can hear that the cycles preview is 
active (independent of rendering or finished with rendering).

Why is the fan not slowing down after the preview has finished rendering?
Maybe the preview is refreshing the image with maximum FPS independent 
from the rest of Blender UI?
How can I check the GPU workload, to have some valid values to confirm 
my observation?

Can someone else confirm this on other systems?

Happy blending,
Conz