gnome-shell on Wayland is very sluggish when using an eGPU
When using the display output of a Thunderbolt external GPU, the gnome-shell Wayland session is very sluggish. Frame rates are low, the mouse pointer is lagging, and I get especially low frame rates for any app that I'm running on the eGPU with DRI_PRIME=1
. I'm not sure what is going on here, but I have the impression that this happens because the compositor is copying frames between the integrated GPU and the external GPU back and forth.
Hardware is a Dell XPS 13 9370 with an AMD RX 570 in a Zotac AMP box mini.
As far as I see the Wayland session can otherwise handle the eGPU much better than X, aside of the sluggishness.
(Trying the same setup with Xorg is broken in different ways. When I try to start an Xorg session with the eGPU plugged in without any manual configuration then Xorg straight out crashes. If I run an Xorg session with a config file where I explicitly tell X to use the AMD GPU then it works pretty decently but then X cannot handle unplugging the eGPU.)