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    SubjectRe: [Fwd: Re: [patch] Real-Time Preemption, -RT-2.6.9-mm1-V0.4]

    * Ingo Molnar <mingo@elte.hu> wrote:

    > > removing the poll() lines doesnt seem to impact the quality of the
    > > data, but i still see roughly 50 usecs added to the 'real' latency
    > > that i see in traces.
    >
    > this i think is related to what Thomas observed, that there's a new
    > irqs-off critical section somewhere. (it's in the new priority
    > handling code i think.)

    ah, found it. Only RT tasks were supposed to get special priority
    handling, while in fact all tasks got it - so when Thomas ran hackbench
    (Thomas, you did, right?) it created an O(nr_hackbench) overhead within
    the mutex code ... I've uploaded -V0.6.5 to the usual place:

    http://redhat.com/~mingo/realtime-preempt/

    Thomas, can you confirm that this kernel fixes the irqs-off latencies?
    (the priority loop indeed was done with irqs turned off.)

    i'm not sure this fix is related to the deadlocks reported though.

    Ingo
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