Ubuntu 18.04 systemd-udevd uses high CPU, conflict with nvidia graphics
I solved this problem by running
sudo mv /lib/udev/rules.d/71-nvidia.rules ~
and rebooting, so that udev doesn't try to load the nvidia module.
So far, so good, though I suspect this has probably done something to the graphics that I won't be aware of.
Workaround
Soon after booting, run the following commands:
sudo systemctl stop systemd-udevd systemd-udevd-kernel.socket systemd-udevd-control.socket
sudo systemctl start systemd-udevd systemd-udevd-kernel.socket systemd-udevd-control.socket
It worked in my Dell laptop, and all the problems are gone.