gnome-shell high CPU usage (~100% CPU1) in idle with external monitor

[Tuan Ho]

i7-8750H (6 cores, 12 threads)
32GB DDR
GTX 1070 Max-Q
500GB SSD
4K external monitor (Dell U2718Q)

No problem without the 4K monitor hooked up. When it is hooked up, CPU1 ~ 100% in idle. Gnome-shell and Xorg the problem.

nvidia 410 from nvidia-ppa.

ProblemType: Bug
DistroRelease: Ubuntu 18.04
Package: gnome-shell 3.28.3-0ubuntu0.18.04.2
ProcVersionSignature: Ubuntu 4.15.0-39.42-generic 4.15.18
Uname: Linux 4.15.0-39-generic x86_64
NonfreeKernelModules: nvidia_modeset nvidia
ApportVersion: 2.20.9-0ubuntu7.5
Architecture: amd64
CurrentDesktop: ubuntu:GNOME
Date: Tue Nov 27 00:22:13 2018
DisplayManager: gdm3
SourcePackage: gnome-shell
UpgradeStatus: No upgrade log present (probably fresh install)

[Launchpad Janitor (janitor)]

Status changed to 'Confirmed' because the bug affects multiple users.

[Daniel van Vugt (vanvugt)]

Can you please try downgrading to a supported version of the nvidia driver:

  https://launchpad.net/ubuntu/+source/nvidia-graphics-drivers-390

and tell us if the problem still happens?

[Daniel van Vugt (vanvugt)]

Actually the best thing to try first is to remove all gnome-shell extensions. You have a few:

b'org.gnome.shell' b'enabled-extensions' b"['<email address hidden>', '<email address hidden>', '<email address hidden>', '<email address hidden>', '<email address hidden>']"

[Tuan Ho (drnoob13)]

I had tried removing everything gnome-related, including the gnome extensions, but it didn't help.

The bug solved with System76 engineers patching their system76-driver.
https://github.com/pop-os/system76-driver/issues/74

[Daniel van Vugt (vanvugt)]

Thanks. If the fix is in 'system76-driver' then I don't think there's any way for us to track that because it's not an official Ubuntu package.