Slow material editor in 4.6

In UE editor 4.6, the material previews in the Material Editor take as much as 10 seconds to update, making iterating on effects cripplingly slow. How do I speed this up? It seems like this was much faster in older versions of the editor.

What helped speed up my material editor and shader compiling very, very much was to set the priority of the editor and the shadercompileworkers to high in taskmanager