The previous default scheduler in the Linux kernel was the Completely Fair Scheduler (CFS).
The core idea of ​​CFS is to maintain a “balance” between tasks using CPU time. When a task is given available time that lags behind others, the scheduler will compensate for this and give it more execution time.
So how does CFS define “balance”? Are there any quantitative standards? What tools can I use to test the fairness of a scheduler?

I know there are tools like eBPF that can test the kernel.
Does eBPF have any directives to test fairness?