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    SubjectRe: RT task scheduling

    * Bill Huey <billh@gnuppy.monkey.org> wrote:

    > The last time I looked at it I thought it did something pretty
    > simplistic in that it just dumped any RT thread to another CPU but
    > didn't do it in a strict manner with regard to priority. Maybe that's
    > changed or else I didn't pay attention to it that as carefully as I
    > thought.

    well as Darren's testcase shows, it might still have some bug - but the
    mechanism is intended to be strict. (the implementation had a couple of
    strictness bugs (they show up as long latencies on SMP) but those were
    ironed out months ago.)

    > As far as CPU binding goes, I'm wanting a method of getting around the
    > latency of the rt overload logic in certain cases at the expense of
    > rebalancing. That's what I ment by it.

    yeah, that certainly makes sense, and it's one reason why i'm thinking
    about the separate SCHED_FIFO_GLOBAL policy for 'globally scheduled' RT
    tasks, while still keeping the current lightweight non-global RT
    scheduling. Global scheduling either means a global lock, or as in the
    -rt implementation means a "global IPI", but there's always a nontrivial
    "global" cost involved.

    Ingo
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