[ivlad]

I vaguely remember Solaris had a way to prioritise focused X Window application (IA) while keeping it within time-sharing (TS) scheduling class.

Kernel thread for interactive applications in focused window would then have higher priority than background applications improving responsiveness. I am not sure what manipulated the priority, but I assume Xsun (X Window server) did it.

[worthless-trash]

I believe that this absolutely could be done with ebpf setting schedule priority. A small daemon looking at the front-running window and you're there.

https://lwn.net/Articles/873244/