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    SubjectRe: [patch] voluntary-preempt-

    * Lee Revell <> wrote:

    > Also I have noticed a pattern with the XFree86 schedule() latencies,
    > they all have a section like this:
    > 04000002 0.003ms (+0.000ms): effective_prio (recalc_task_prio)
    > 04000002 0.003ms (+0.000ms): enqueue_task (schedule)
    > 00000002 0.006ms (+0.003ms): __switch_to (schedule)
    > 00000002 0.088ms (+0.082ms): finish_task_switch (schedule)
    > 00010002 0.090ms (+0.001ms): do_IRQ (finish_task_switch)

    > I presume the 04000002 -> 00000002 is some interrupt being unmasked
    > (or interrupts being globally enabled), then there's a 60-80 usec
    > latency in schedule().

    0x04000000 is PREEMPT_ACTIVE - which is just a bit we set to make sure
    we dont try to preempt recursively.

    but the XFree86 latency is interesting indeed. It could be the effect of
    the now-enlarged ioperm() bitmap! 80 usecs is excessive.

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