ROS 1 is said not to be able to run RealTime. Still, you can switch your linux kernel to RT preemptive mode and set rtprio to the ROS launch, so that the ROS and Gazebo processes run with some Real time priority.

What would happen?

When I try it (Gazebo 11, ROS noetic) with rtprio value larger than 50, the computer just freezes. Why does it happen? Is there any way how to make it work?

I'd like to understand this in better detail.