Issues with Ubuntu 16.04.2 with kernel 4.8

[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.

[giuliocoluccia]

I'vre tried your workaround but id did not work. But I may have done something wrong. Here's what I did. I edited the file /usr/share/doc/xserver-xorg-video-intel-hwe-16.04/xorg.conf which looked like this:

Section "Device"
	Identifier "Intel"
	Driver "intel"
#	Option "AccelMethod" "uxa"
EndSection

and I replaced it with your code. But maybe Card0 and the bus address are not correct on my machine, or I've edited the wrong file. Can you help me with that?
Thank you

[jerrinot]

I actually used `# Xorg :1 -configure` to generate a config file. Strangely enough it did generate a config file with the intel driver not the the modesetting driver. Then I just copied this file into /etc/X11/xorg.conf

It's using the old(?) config style where all options are in a single file, so perhaps it's not very future-proof and it might break with another update. For a reference, here is the generated file.

[DesertF0x]

I am getting around the slow graphics when I am turning on the Laptop display additionally. But I always have to reconnect the dock after X started. Things were working with 4.4 and older driver.