SUMMARY
This bug was experienced on a clean install of Windows 10 22H2.
Windows 10 Pro - OS buildversion : 19045.2130
All drivers are up to date, and the issue is specific only to Krita among my art programs.
All my other art programs are working fine, including Photoshop.

STEPS TO REPRODUCE
1. Open an A4 blank canvas.
2. Make sure you have a limit of 400 undo steps set from the settings.
3. open the undo history docker and keep it in display somewhere on the UI.
4. make tiny strokes on the canvas and fill it scrupulously until the undo steps is full.
5. check the for the render delay of the brush cursor everytime you release your pen after a stroke.
6. Try to hold the Undo/redo after the history is full.


OBSERVED RESULT
1. At a certain moment, the cursor starts to briefly stutters after each stroke( undo steps filled at about 300 or more ).
2. Once the undo history is full, every time you lift your pen as you perform strokes, Krita stutters for about half a second..
3. The undo/redo operation is ten times slower when the undo history is full. And when you hold either shortcut, you notice stutters as well, as your strokes are undoing/redoing themselves

EXPECTED RESULT
1. No  stutter at all or notice of performance reduction while undoing/redoing.
2. No stutter at all just when you lift your pen after a stroke.
3. Krita's performance should remain as if the undo history was empty.


ADDITIONAL INFORMATION
Krita performance settings : 
1. RAM 
Memory limit : 4096 MiB
Swap Undo After : 512 MiB

2. Swap File
Size Limit : 8GiB

The bug was tested and consistent in Krita 5.1.0 beta2, Krita 5.1.0 to Krita 5.1.3 stable.