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    SubjectRe: new IRQ scalability changes in 2.3.48

    On Sun, 12 Mar 2000 yodaiken@fsmlabs.com wrote:

    > > Quite regardless of how you do interrupts: it doesn't matter where youput
    > > the ACK's, you always need to make sure that irq masking etc is correct,
    > > and you must NOT allow a context switch while an interrupt handler is
    > > still running.
    >
    > Ok. Ingo: does your "low latency" patch violate this rule?

    yep, of course. It's a grave error to schedule during IRQ contexts, and we
    do have an assert in schedule() so it's plain impossible. The lowlatency
    patch simply works by increasing the effective frequency (occurance) of
    rescheduling (preemption) points [without actually rescheduling more
    often].

    Having said this, i now do agree that doing a preemptible kernel (which
    the Linux SMP kernel could become with a small amount of work) is a
    superior solution to this, wrt. latencies.

    Ingo


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