Note the cycles-x builds on builder.blender.org are made with an older CUDA toolkit version. We got better performance with CUDA toolkit 11.3, and that’s how both master and cycles-x were built for the graphs in the blog post. We’ll upgrade the buildbot CUDA toolkit to fix this.
I don’t know how big the differential is exactly, I didn’t test recently.
The barbershop can be compared by removing the ENV-Fog.001 object.