I just updated to 20w22a, and my average framerate dropped to around 10 FPS. When I played my world in 20w21a, I used maximum shading, fancy clouds, bobbing on, set my render distance to 15 chunks at 1080p and could crank out 40-50 FPS at all times. As soon as I updated the world to 20w22a, Minecraft was basically unplayable. I turned every fancy graphics setting off, lowered my render distance to 5 chunks, made the window smaller, and could only get about 10-20 FPS. I assume this has something to do with the 'experimental graphics rendering' introduced in the new snapshot.