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    SubjectRe: [patch] Real-Time Preemption, -RT-2.6.9-mm1-V0

    * Ingo Molnar <> wrote:

    > > Still problems with interactive behavior. Running KDE, with top
    > > running in xterm, scrolling through the menus I get some pauses. When
    > > the pauses occur I see kdeinit hit the top of the list and sometimes
    > > consuming 90% or more of a CPU and idle usage drops to 30-40%. I do
    > > see some latency traces (not really high ones) in the log that were
    > > generated by kdeinit but I think they were generated prior to when
    > > these pauses occurred, most likely when logging in.
    > is this 90% or more CPU time system (kernel) overhead or userspace
    > overhead?

    another thing to watch for is the context-switch rate in vmstat. -V0.3
    patches include a hack that include involuntary context-switches (mutex
    context switches) in the context-switch stat as well. (previously those
    were reported in a separate field which vmstat didnt pick up.)

    So if the context-switch rate shots up to above say 100K/sec that is a
    sure sign of some mutex badness. The livelock scenarios i solved in
    -V0.3 occasionally generated a more than 500K/sec context-switch rate on
    a 2GHz box. Having just a couple of thousand per sec isnt by itself a
    sign of anything unusual.

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