Issues with Ubuntu 16.04.2 with kernel 4.8

[giuliocoluccia]

I'm more and more convinced that this is a software issue. I've tried to connect my docking station to another pc not upgraded to kernel 4.8. No errors in the syslog related to the cable. Then I've plugged it again to my laptop and the monitor woke up. No errors in the syslog related to the cable. But still unusable (very slow, high cpu usage by DisplayLink server). I attach the report of the Support Tool.

[mlukaszek]

I am trying to get my head around it
Could you please clarify one thing: do I read correctly that this happens when you close the laptop lid (so the built-in screen is off)?
If yes, is the same problem visible when you keep the lid open (and do not disable the built-in screen)?

Cheers,
Michal

[giuliocoluccia]

This is what it looked in the first place. I tried again this morning (the kernel updated, I hoped this was fixed) and it seems that the problem arises just connecting the external monitor, no matter if the lid is on or off. The problem is significantly amplified when I open Google Chorme, which is unusable. If I unplug the external monitor or I connect it with the displayport, everything works fine.

[giuliocoluccia]

Let mi know it there's any test I can run to help you understand. Thank you!
I hoped that this morning's update of kernel and hardware enablement stack could fix the issue but still no luck. I attach the report of the support tool.

[jerrinot]

Hello,

I'm also running Ubuntu 16.04.2 with the 4.8 kernel and I'm experiencing massive slowdown as well. I tried to upgrade the driver to the version 1.3.52, but it made no observable difference. Chrome is really unusable, even gedit is super slow.

I believe I was on 4.8 kernel even before and it worked fine. The slowdown happened when I enabled the full Ubuntu HWE stack and Xorg got upgraded to a newer version.

glxgears reports 1 FPS when I move the window to a display connected via DisplayLink. Unfortunatekly I don't know FPS before the HWE upgrade.

[giuliocoluccia]

Originally Posted by jerrinot

Hello,

I'm also running Ubuntu 16.04.2 with the 4.8 kernel and I'm experiencing massive slowdown as well. I tried to upgrade the driver to the version 1.3.52, but it made no observable difference. Chrome is really unusable, even gedit is super slow.

I believe I was on 4.8 kernel even before and it worked fine. The slowdown happened when I enabled the full Ubuntu HWE stack and Xorg got upgraded to a newer version.

glxgears reports 1 FPS when I move the window to a display connected via DisplayLink. Unfortunatekly I don't know FPS before the HWE upgrade.

I confirm each and every symptom. And the same happens if I boot Ubuntu with the 4.4 kernel choosing it from GRUB.

[jerrinot]

Interestingly enough the slowdown appears to be caused by the modesetting driver the new Xorg uses for Intel cards by default!
I explicitly configured the old driver in my xorg.conf and it seems to work fine again!

Section "Device"

Identifier "Card0"
Driver "intel"
BusID "PCI:0:2:0"

EndSection

Apparently there is some bad interaction between the modesetting and DisplayLink drivers. This should be addressed as the modesetting thing is now default in many distributions.