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    SubjectRe: [patch] Real-Time Preemption, -RT-2.6.10-rc2-mm2-V0.7.30-2
    Ingo Molnar wrote:
    > * Eran Mann <emann@mrv.com> wrote:
    >>
    >>Hi,
    >>I´m seeing latencies of up to ~2000 microseconds. see attached traces
    >>file for a small sample. I think I´m missing something obvious
    >>config-wise but I don´t know what...
    ...

    > this seems to imply IDE DMA related hardware overhead. Apparently what
    > happens is that with certain motherboards/chipsets, if IDE DMA happens
    > then that DMA transfer _completely locks up_ the system bus. Nothing
    > happens, and the CPU is stalled in essence until the end of the DMA
    > request.
    >
    ....
    > Ingo

    Right on.
    After hdparm -d0 I see maximum latency of 35 us after a full kernel
    build with a few GUI apps in the background. I´ll try to find a
    reasonable compromise.
    --
    Eran Mann
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