What is Composition PreLighting

I am trying to optimize a game for VR and I keep seeing this under my “stat GPU”.

My entire scene is static lighting, but there is quite a bit of instanced foliage with opacity masking.

So far in all my searches I have not seen any clear indication of what is happening in this section, and

+1, Same question
It takes 3-4 ms to render the frame in a simple scene

It’s the issue of umg , you can remove all of you umg from viewport, and have a try.

I can’t confirm this. I have exact the same problem and removing all widgets doesn’t fix this for me. Removing doesn’t have an effect at all for me. What exactly is this Composition Prelighting and what can be done to lower its impact?