Windows 10 being a spyware app should still not affect performance that much. Seeing that gaming didn’t drop by 1/2 even in CPU intensive games indicates that there is something else going on. And in one scene (Fishy Eye) Windows 10 was actually faster then Windows 7 (depending on the GPU that is)
Part of the everlasting issue is that Blender Developers are more Unix oriented so issues like this are not their priority. They have only a Blender Bot that complies Windows version for them, but as they do not use it for their production on daily basis, they might not even see the performance drop and have time to start investigation around it.
They did just “received” Windows 10 buildbot when Windows automatically updated it without them knowing. And the only reason they knew it changes is that people contacted them that they are not receiving Windows builds. Sadly confirming they don’t have much interest in Windows platform.
It could be a complier issue, just as it was in the earlier days with miniwig (was that the name) vs MS Visual C which did give Windows a significant rendering boost.
Personally I’m happy with Windows 10 for everything else that I do on it. Rendering… yeah, kind of bummer. Might have to “build” a Unix based renderfarm …
Still hoping Developers will find time to investigate and resolve the performance issue…