How to limit CPU usage with systemd-run

I have a buggy program which uses 100% CPU even when it's idle. Since fixing it isn't practical at the moment, I'd like to just limit it to be able to use no more than 10% CPU. However no matter what I do, the process always chews up 100% of one CPU. I found instructions on the [Arch Wiki](https://wiki.archlinux.org/index.php/Cgroups) that tell me to create a file containing this: # cpulimit.slice [Slice] CPUQuota=10% Apparently I can then launch a shell using these limits, like this: systemd-run --slice=cpulimit.slice --uid=myuser --shell This seems to work and after entering in my sudo password I get a shell, so I run a simple test that will use 100% CPU and I can stop with Ctrl+C: while true; do true; done I expect this to use no more than 10% CPU since it's running inside the slice, however it always uses 100% CPU! What am I doing wrong?