Ubuntu 16.04 Guest - Severe UI lag when starting VM in fullscreen vs. fullscreen after boot

[pgrohe]

Hi there,

To start, my setup is as follows:

• Dell XPS 13 9350 / SkyLake i7 6560U / 16GB RAM / 3200x1800 'HiDPI' display / Intel Iris 540 GPU using i915 driver
  Ubuntu 16.04LTS Host w/ Kernel 4.6, VirtualBox 5.1, DKMS installed before VirtualBox install
  Ubuntu 16.04LTS Guest w/ Kernel 4.4, DKMS installed, Guest Additions Installed, 128MB VRAM, 8GB RAM, 2 CPUs assigned, 3d Acceleration Enabled and confirmed with /usr/lib/nux/unity_support_test -p, Fullscreen resolution 3200x1800

I have observed severe UI rendering lag & input lag on my VM and have been wracking my brain trying to figure it out. Specifically, opening the Unity Launcher on Ubuntu is very slow during, it 'fades in' over 1.5 seconds or so. Once it's open typing in the search bar also lags very severely behind the actual physical typing. It's not just the Unity Launcher, all other applications have the same severe lag, both graphically and input.

Just a moment ago I noticed something interesting regarding this. If I boot up my VM in windowed mode performance is good & UI is responsive. It remains responsive if I switch to fullscreen afterwards. However if I boot directly into fullscreen (i.e. it was in fullscreen when I last shut it down) the above mentioned poor performance is present. Switching back to windows mode once it is occuring does not resolve it. Shutting down the VM while windowed, rebooting windowed and then switching back to fullscreen does set things back to normal.

EDIT - I've also tried with just 1 CPU allocated to the VM and the issue still occurs as described.

Does anyone have an idea what would be causing this & what may be the fix? It's not too bad to make sure to just start it windowed but I'm wondering if it's a symptom of another underlying problem.


Thanks!

Attached Files:
vboxlog.zip - ZIP of VBox.log from the Virtualbox GUI for the Guest in question
cpu-info.txt - Info on CPU of the host
unity_support_test.txt - Output of /usr/lib/nux/unity_support_test -p for both the Host and Guest

[bubbleboy]

I had the same problem as you, sluggish 16.04 but with a windows 10 host. I tried starting it windowed and then going to fullscreen. Problem gone! My machine is a ASUS UX305 with 3200x1800 resolution.