Scene edit performance 5 FPS at max. GI buggy. (Case 736077)

Please start testing Unity on bigger projects, we hit more and more bugs with every new unity release. Even the new job system + multi threading seems to be hogging systems down instead of improving performance.
We'd happily share our project Verdun to this end but would need a point of contact to work together on these Unity bugs.

(Case 736077) Editor scene editing too slow due to GISceneManager.Update

When opening any of our scenes, the editor is very slow because GISceneManager.Update is running at 200-500MS according to the profiler (We are NOT even using GI). After 10+ minutes it will stop and the scene editing performance is back to normal again. However, (saving) and reopening the scene it will ALWAYS trigger this GISceneManager.Update again for 5 - 15 several minutes.

(Case - none yet) Jobs system is hogging systems down instead of improving performance. Performance goes down with every extra multi threaded component

Making a repro case today.

 

As for the slow edit performance:
This is not a 5.3 specific problem but has been around since 5.2 and possibly longer.
The Case 736077 contains a 4gb repro project: just open the project and you'll experience the unworkable lag in the scene view right away.

We do have a lot of materials (100-330 or so?) on about 50.000 mesh renderers per scene (LODs included though)

My biggest question for this perf. problem is why it is running at all, since we arent using GI since it was never working on our setup (used to crash, havent tried recently)

 

I'm working on the levels of Verdun. From my experience, the performance problems have been there at least since around June this year. At times when running the editor for a while the performance gets a bit better but never really good enough to get a nice workflow. The current scene I am working on had a scene of approximately 60 MB when the slow downs started to bother me. The other production scenes average around 150 MB. I also observed when performance is slightly increased after using the editor, going in and out of play mode the performance drops back down.

This problem is really impacting the workflow since we're working with the terrain tools a lot the low FPS limits the input of the terrain tools so that it's messy to draw a sculpt a smooth bank with the height tool, or drawing a texture across the terrain gets all stuttery. Also just moving the camera through the scene can be a hassle, it stutters and lags a lot and at times just sort of launches itself far out of the scene. I also suspect some of the problems we're having with selecting prefabs are to blame on performance.

 

This is the actual culprit: