Benchmark method

1. Create a new world with only the Fabric loader installed
2. Don't move the camera or player at all
3. Wait for a few minutes for TPS to stabilise and take screenshot
4. Install only Bewitchment and its required dependencies
5. Load up the same world and repeat steps 2-3

Results

Fabric Loader

Bewitchment + Required Dependencies

This may be due to one of Bewitchment's many dependencies however I think it should noted anyway and this issue should remain open until resolved.

Tested with only Pehkui and Fabric API. Doesn't look like it causes the issue when by itself at least.

Can you also test this with only Pehkui installed? I've seen people say Pehkui causes lag

I see. Can you also test with all of the dependencies but not including Bewitchment?

The mspt still seems to hover around 8.

It could still be an issue resulting from a dependency that has a part that does not "activate" unless being used by a mod though. I think more in depth profiling is needed to determine the cause.

I did a simple profile with spark and nothing really looks bad to me at least.

Does this still happen in 1.17-7? There should have been a large performance boost

There does seem to still be a performance impact, however it does seem slightly less now.

Fabric Loader

Bewitchment

I'm not really sure if this is something I can fix, it seems necessary for the mod's functions

Same here, when I use Pehkui on my modpack, it eats literaly all server resources making it unplayable. It seems to update the sizes of every loaded mob every game tick. It whould be nice to have an option to disable it even if the resizes of some mobs are lost

Yeah, this looks like Pehkui is just resource intensive and I can't really do anything about that. I'd recommend submitting this to their repository and see if they can optimize it