Ubuntu Gnome 16.10, Kernel: 4.8.0-45-generic, GPU Drivers: Kabylake GT2 (i915) Version: 2:2.99.917+git20160706-1ubuntu1, one attached monitor (1080p Dell 23") via DP.
As far as I can tell, GPU acceleration is either barely used or just not used at all via the Thunderbolt port. Youtube videos peg all 4 cores on the i7, and still sound is off-sync. Performance is marginally better on the laptop screen rather than the external monitor, but that kind of defeatsthe purpose of the dock. Chrome in general is being super CPU intensive and lagged while the dock is plugged in, usually smooth as butter when not plugged in.
Using the info here I did manage to get all the USB ports working (by turning off TB security), but having web pages with intensive JS gum up my browser is pretty awful. Even with the supplied 16.04 and Unity it wasn't great. I won't even go into the uselessness of the DA200 and the joys of having to run xrandr every time I restart Gnome (since that seems to be a general linux HDPI problem).
I have seen people mention firmware updates, though how one is supposed to do that without MSWindows doesn't seem to be anywhere. So what's up Dell? Do we get any sort of real support/updates?
I love the laptop itself, but why can't we get some reasonable dock (or any) support?? At least give us some driver packages or recommendations or something. You recommend peripherals that work shoddily or not at all, and say they are compatible, offer updates I can't install, and no real support in your website support section. That's pretty ***. I'm not trying to go on a real rant, but your company makes millions selling this stuff to developers at major institutions like mine, put some of that money into supporting your product.
I have probably the same issue as you, wether or not I have a monitor attached. I have the QHD+ monitor. The system cpu % is too high in comparison with older dell laptop I have. My lattitude 7440 runs much smoother...
I am actually wondering if the i915* kernel modules are the culprit, but I have been unable to pinpoint any kind of metrics that would strongly back this up.