System unresponsive even when running command with nice

Debian 10. I am trying to render with blender in the background, like so: nice -n 19 blender -b --python my_script.py This renders to a file using the GPU. When rendering, I can see GPU usage spike to 100% with nvidia-smi, the system load goes up to around 3, and with top I can see cpu usage go to 110% for both blender and xorg. iostat shows almost zero iowait. At this point, my system becomes almost completely unresponsive. Windows take 10 seconds or so to get focus, etc. If I do ctrl+z, after 10 seconds or so the signal is processed and as soon as blender is suspended, my system instantly returns to normal. My end goal is to render in the background on my workstation while keeping my system responsive. How do I accomplish this?