System Information
Operating system: Windows 10 64 bit
Graphics card: Nvidia GeForce 750 Ti

Blender Version
Broken: Blender 2.80, 4c31bed6b46, blender2.8, 2018-11-30
(example: 2.79b release)
(example: 2.80, edbf15d3c044, blender2.8, 2018-11-28, as found on the splash screen)
Worked: (optional)

Short description of error
When I add a Subsurface Modifier and then adding Loop Cuts it starts lagging until I place the Loop Cut.

Exact steps for others to reproduce the error
Based on the default startup or an attached .blend file (as simple as possible).