System Information
Operating system: Win 10 home
Graphics card: Gtx 970

Blender Version
Broken: 2.80 Beta
Date 2019-01-04 a77b63c56943

Short description of error
Adding Subdivision Modifier to a cylinder with n-gon caps is too slow.
It work Ok if the cylinder is all quads
Exact steps for others to reproduce the error
Add a cylinder go edit mode subdivide a few times , back to object mode and try to add Subdivision modifier
Based on the default startup or an attached .blend file (as simple as possible).