NOTE: THIS BUG HAPPENS IN VANILLA, DO NOT DISCOUNT THIS POST SIMPLY BECAUSE I TESTED WITH OPTIFINE, SODIUM ETC. I made a previous post on the exact same issue (MC-207911) which got falsely resolved because I wasn't using the vanilla client and was using optifine instead.

When playing, the game microstutters every so often from versions 1.15-1.16.4. After extensive testing I've found that this happens around every time the java memory collection (seen in the 2nd line of the top right of the f3 debug screen) is cleared. I've tested previous versions (1.12.2, 1.13.2 and 1.14.4) and found no stuttering problems with them. Other games I play do not stutter either, meaning that it is extremely unlikely that it is a hardware problem on my end. My issue is exactly the same MC-178007, except for me this happens in both singleplayer, multiplayer and realms.

For reference, my specs are a Ryzen 7 3700X, GTX 1080ti (driver version 456.98), 32GB Ram 3200mhz cl16, using a 240hz monitor, and all temps are fine during gameplay. I normally play with my render distance set to 8 and v-sync turned OFF.

What I've tried:

• Allocating 4 and 8 gigs of RAM respectively
• Setting minimum amount of RAM to 128mb (using the JVM argument xms-)
• Changing the render distance to 2, 8 then 16
• Enabling V-sync both in game and in Nvidia Control Panel 
• Testing vanilla minecraft, with optifine installed, with forge, with fabric+sodium AND with Badlion Client (microstuttering still persists in versions mentioned)
• Deleting the .minecraft directory and reinstalling Minecraft
• Deleting the .minecraft directory AND uninstalling the Minecraft launcher, then redownloading everything
• Reinstalling Nvidia drivers to the newest version as of today (457.51)
• Reinstalling Nvidia drivers to an older, more stable version (456.98)
• Resetting/reinstalling Windows (I have windows 10 Pro N installed) and performing a clean install of Minecraft to make sure it wasn't an external factor causing this issue

TLDR: after extensive testing I've determined that the microstuttering happening in versions 1.15 and above seem to be a coding bug. Slicedlime or anybody else, I'd really appreciate if you'd fix this as its driving me nuts. Info can be found in the attachment below and examples can be found in these two videos: https://www.youtube.com/watch?v=aOakQDt_aHs and https://youtu.be/lXq-5rzrHKE?t=97. Thanks for reading.