VERY poor performance 4k performance on Ubuntu

I have a AskUbuntu post on this as well… [url]graphics - 4k Nvidia performance on Ubuntu - Ask Ubuntu

Fresh Ubuntu 16.04.1 install, have used both a GTX960 and a M4000, 4k@30Hz monitor, the graphics performance has been terrible. I’ve had to disable VSync and Chrome GPU acceleration to make my machine useable for normal use. If I add something else like a Steam game running the GPU grinds to a halt.

This YouTube video

gives an example of the freezing. It looks like it has an extremely hard time context switching between windows or GPU tasks, taking a few seconds or more.

I am currently on the 367 drivers from the Ubuntu repositories, but I’ve tried everything from 352 to 370.

My previous system was a simple Gigabyte Brix Pro running a 4770 with Intel Iris Pro Graphics, and that simple integrated GPU had absolutely no problems running these same tasks. This GPU I should be able to run 4x 4k@60Hz monitors no problem, not dying to run one at half the frame rate!