SMP, and the case for pinning a core

Multiprocessing is solid across the eight cores now, with everything scheduled pre-emptively.

What I would like next is the ability to force a core into a real-time mode - no pre-emption, one job, and nothing else scheduled on it - while everything else carries on being scheduled as it is today. The two would coexist rather than replace one another.

Radio-related peripherals are the motivation. A device with a hard timing requirement does not care that the scheduler is fair, it cares that a deadline is met every time, and the cheapest way to promise that is to stop sharing the core. Eight cores is enough that giving one away costs little, and the alternative is a scheduler that has to be right about latency in every case rather than a core that cannot be interrupted in any.

Nothing is built. At this point it is an idea and a note to myself, and the honest test of it will be whether some piece of hardware I am already fighting turns out to need exactly this.