As you can see in the screenshots below the frame rate is heavily affected by chunk updates (not really the updates but more the loading/unloading and generation of chunks). I'm guessing that this has to do with the reworking of the engine in the newer snapshots of the game. I hope you look at it and try to fix it.
- duplicates
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MC-123779 When the new chunks are loading the client create huge lag spikes in singleplayer.( when loading 5-20 FPS, when loaded back to normal 50-60 fps.)
- Resolved