Answer by Hasan Sh for systemd-journald high CPU usage

@S_n Can you please check the logs, and see whether it gives indication about the problem?

I've had the same problem and that caused to an infinite loop, and the cpu was constantly higher then 30%.

So if you run in the terminal journalctl you can check it the log in the terminal.

I fixed it by adding a pci=nomsi parameter to the GRUB_CMDLINE_LINUX_DEFAULT property(you can find and edit it in: sudo vim /etc/default/grub)

After adding the parameter update the grub: sudo update-grub and then reboot. Then run top in the terminal, and see whether that fixed it.

Note: By doing that you'll add the parameter permanently, however you can do it temporarily

If you want to add it temporarily, as following:

1. Start your system and wait for the GRUB menu to show (if you don't see a GRUB menu, press and hold the left Shift key after starting the system).
2. Now highlight the kernel you want to use, and press the e key. You should be able to see and edit the commands associated with the highlighted kernel.
3. Go down to the line starting with linux and add your parameter pci=nomsi to its end.
4. Now press Ctrl + x to boot.