Profiling a gradual Editor slowdown?

I’m experiencing a gradual Editor slowdown. After a few Plays and some time spent in the game (inside the Editor), the game runs considerably slower and finally gets to the choppy 10 FPS. Real FPS - measured with a separate script - fall down and as the game gets slower, the FPS estimate given by the Stats window gradually gets higher. The Profiler doesn’t show any performance issues.

Restarting the Unity Editor helps. Game runs super-smooth after an Editor restart, then after a time it slows down. Restarting the game in Editor doesn’t change a thing - it’s still slow after a restart. Only restarting the whole Editor does help.

I didn’t manage to test if I happens in the build, but all the traces lead to some kind of Editor performance leak. It most surely isn’t a memory issue - I experienced the slowdown when Windows Task Manager displayed very low memory use.

How should I approach debugging and profiling an Editor performance issue?

Are you doing any editor scripting at all? If that’s the case, you might have a memory leak in one of those scripts - say a custom view that keeps adding elements to a list or something along those lines.

Anyways, to profile the editor, open the Profiler window (Window/Profiler), and select “Profile Editor”. That’s only available on pro, so if you’re on free, no such luck.