Lagging video in fullscreen

[Vael_S]

Window Manager Tweaks, then turn off the composer and turn it back on.
This fixed many video lag issues I found.

If it’s not related to the composer, then check the RAM utilisation and assignment to the guest. You may be maxxed out using a resource hog like Firefox or Chrome.

If this does not work, then you may find you need to set the VideoRam for the machine. If it’s a standard guest you can do this using something like the following…
qvm-features GUESTVM gui-videoram-min $(($WIDTH * $HEIGHT * 4 / 1024))
qvm-features GUESTVM gui-videoram-overhead 0

otherwise, referr to the following.

Debian HVM - small screen resolution

Ok, I was able to fix the issue with resolution by increasing the qube’s video ram in Xen config. You can test whatever this will fix it for you as well by running these commands in dom0: sudo mkdir -p /etc/qubes/templates/libvirt/xen/by-name/ cat << 'EOF' | sudo tee /etc/qubes/templates/libvirt/xen/by-name/YourQubeName.xml <!-- import default template--> {% extends 'libvirt/xen.xml' %} <!-- we wanna alter the devices block --> {% block devices %} <!-- import default device block --> {…

This will set the VRAM as well.

Other than that, could use VirtualGL

Seamless GPU passthrough on Qubes OS with VirtualGL

We are presenting to you a guide regarding GPU passthrough created in collaboration with peers. Qubes OS already has extensive documentation available about GPU passthrough for 3D accelerated tasks but they all require in depth configuration, extra displays, and extra input devices. With VirtualGL (https://virtualgl.org) one can take advantage of the existing Qubes OS framework for audio/display by offloading OpenGL onto the secondary graphics card directly with VirtualGL. This document will mo…