@priort yes, odd, isn’t it? And that’s with a NVidia GTX 1080, which is not a slow GPU at all. In general, OpenCL is really only a modest performance improvement.
Looking into the timings in more detail, I noticed that half the rendering time is spent on updating the preview. As far as I understand, that’s the little thumbnail in the top left. If we could speed up darktable by a factor of two by not showing that thumbnail (or updating it less often), that would be a tremendously worthy tradeoff in my book.
Does anyone know if that’s indeed how it works?