I recently upgraded my large-scale RPG world project from 2019 LTS version to 2021 for the native Silicon support. I have a Silicon based Mac and even though the game seems to have smoother FPS in the 2021 builds, the lag spikes are extreme.
These lag spikes, after profiling, come from the method DynamicGI.UpdateEnvironment() which is called a few times a second. Even when I increase this interval the lag spikes just make the game jittery despite the overall smooth FPS.
Why is it that Unity 2021 handles this method so poorly? In my 2019 build I was getting slightly less FPS overall but it was extremely consistent and no lag spikes (Intel build played through Rosetta 2). I checked a 2021 Intel build and same problem, it was smoother overall (less so than the native Silicon build) but had lag spikes.