Developing a Custom DSQ Manager for sched_ext

Linux 6.12 shipped sched_ext — not another scheduler policy sitting alongside CFS, but a framework that lets you replace the entire scheduling algorithm with a BPF program, live, without rebooting. The primitive that makes this work is the Dispatch Queue (DSQ). Get DSQ management wrong and you either leave CPUs starved while work piles up in your custom queues, trigger the watchdog that forcibly evicts your scheduler back to CFS, or silently starve low-priority tasks until your batch jobs stop making progress entirely.