I could be wrong, but when you do profiling while running even an empty scene using 2DRenderer pipeline, I still get some CPU cost going on for the Global Illumination section in profiler. Is this false alarm? Or some GI thread is still running at the background, even, (obvisouly) totally not needed for current 2DRenderer pipeline? Yeah, It's small, but still! It's there? How can I completely disable GI process?