More operation lag when Minecraft is in a higher resolution than 1K

I have a screen of 3440px*1440px (21.5 : 9).

When i run Minecraft not in a fullscreen mode, all things look right.

However, when i truns Minecarft into a fullscreen, my operations lags.

It's hard to discribe.... Like when u type 'W', the character will move towards 1s later after my typing.

 

Idk whether it's my problem or not.

I makes windows to use my discrete graphics card but in the task manager it shows GPU-0.