As you can see from this screenshot GPU usage goes up and down as the current frame is finished rendering and the next frame is prepared. Because the GPU is not needed while the frame is prepared the GPU usage spikes and drops, spikes and drops and so on.
For more detailed renders this wouldn't be a problem, but as each frame only takes 5 seconds to render this basically doubles the rendering time, because of downtime. Is there a way (either theoretically or practically) to make the GPU work constantly? Perhaps by preparing the next frame behind the scenes?
As you can see by the CPU usage, it spikes up and down also, as it prepares the frame to be rendered and then waits for the GPU to render the frame before starting up again.
My thinking is that you could have 100% up time for both the GPU and CPU by having the CPU prepare the next scene while the GPU is rendering the current one. Perhaps similar to how a real time game might work. Right now it seems one is waiting for the other and that seems unnecessary (as far as I can tell) at least after the first frame.