Since upgrading to Monterey (12.0.1) my system (Macbook Pro 2018 running Parallels 17.1) becomes very unresponsive when running Big Sur (11.1) in a virtual machine. Big Sur uses about 10% - 20% CPU in total according to its own Activity monitor, but in Montery, the virtual machine Big Sur takes up between 50% - 100% CPU. The system responds very badly to mouse input and keyboard input (missing many characters). I have reinstalled Parallels Tools and restarted, but nothing helps. I had to change the hypervisor to Apple (Big Sur virtual machine > Setttings > Hardware > Advanced > Hypervisor > Apple), because with the Parallels hypervisor, the virtual machine crashes.