[jerf]

'Is "scheduler cannot give any guarantees" acceptable?'

Most schedulers give far fewer guarantees that you might think. A guarantee to be a guarantee must be true no matter what you do within the boundaries of the language. If you create a goroutine fork bomb

    func fork_bomb() {
        for {
            go fork_bomb()
        }
    }

Go doesn't, to the best of my knowledge, guarantee that any other goroutine will get any execution time, or guarantee much of anything will happen. Your OS is likely to have similarly weak guarantees for the equivalent process bomb, unless you do something to turn on more guarantees/protection.

You have to go into some relatively special-purpose stuff before you can get schedulers that will guarantee that some process will get scheduled for at least 10ms out of every 100ms or something. And then, once you get that guarantee, you'll pay some other way.

Given the fact that most of our machines are incredibly powerful, and that a lot of them still get upgraded on a fairly routine schedule in a lot of dimensions even if single-core clock speed has stalled out, most of us prefer to work with things that just promise to do their best as long as you don't overload them, because the other prices you have to pay to get guarantees turn out not to be beneficial on our monster machines. Of course one should always have their eyes out for when that may not be the case at some point, but in general we're headed away from rigorous guarantees in favor of shared resources that are cheaper and more scalable and making up the difference in volume, rather than trying to get better guarantees.