Ubuntu desktop 20.04 performance issues with Xen

[Mathieu Tarral <mathieu.tarral@xxxxxxxxxxxxxx>]

Hi,

I'm facing concerning performance issues when using Ubuntu desktop 20.04 LTS managed by Xen.

Xen is installed from the Debian package xen-hypervisor-4.11-amd64.

To summarize, the  whole desktop experience feels sluggish.

- connecting via GDM is slower
- typing in the Gnome terminal is slow, and there is an input lag

- sometimes editing files with sudo takes a few seconds before prompting for the password

I didn't expected this as I'm running with the default configuration, and a Xen version stable enough packaged by Ubuntu.

Looking at xl dmesg, i cannot see any indications of misconfiguration.

the Xen command line is

(XEN) Command line: placeholder no-real-mode edd=off

But these parameters are all ignored:

(XEN) parameter "placeholder" unknown!

(XEN) parameter "no-real-mode" unknown!

(XEN) parameter "edd" unknown!

My configuration:

- 5.8.0-48-generic

- 4.11.4-pre

- Ubuntu 20.04 LTS

Any ideas to investigate ?

Thanks