BUG: Extreme Performance hit on PIE with material editor open

I would like to report a potential bug. I have a rather large open world that my team is working on for our game (16k ^2). For the longest time I thought my landscape material, which has a lot of different textures and material functions, was the problem. Today I found that if I had the material editor open, which I did for most of my debugging, the performance for PIE was about 53 ms per frame according to stat unit. When I closed the material editor, this dropped to a much more acceptable 23 ms/frame. Other relevant information: stat slow revealed the total world tick time to be very high, and stat tickables reveals that FMaterialEditor was the biggest hog of call counts and average cycles. I am running version 11.2.

Did you have realtime preview / realtime nodes on in the material editor? If so and it’s a semi-complex material then I’d probably expect a big drop - especially with a big landscape in view too.

Thanks for the speedy reply! I did have live preview and live nodes on, but turning them off did not have any noticeable performance impact. I am still getting about 63 ms/frame with the material editor open.

I would actually like to add that on further investigation the performance drop is with any sort of editor window open, but it is most severe with the material editor open. This is new with 4.11, I am running an i7-4790k 16GB RAM GTX 970 graphics.