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    SubjectRe: [patch] voluntary-preempt-2.6.9-rc1-bk4-R1
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    Alan Cox wrote :
    > On Mer, 2004-09-08 at 21:33, Mark_H_Johnson@raytheon.com wrote:
    > > >.... Please disable IDE DMA and see
    > > >what happens (after hiding the PIO IDE codepath via
    > > >touch_preempt_timing()).
    > >
    > > Not quite sure where to add touch_preempt_timing() calls - somewhere in the
    > > loop in ide_outsl and ide_insl? [so we keep resetting the start /end
    > > times?]
    >
    > If you haven't done hdparm -u1 that may be a reason you want to touch
    > these. To defend against some very bad old h/w where a stall in the I/O
    > stream to the disk causes corruption we disable IRQ's across the
    > transfer in PIO mode by default.
    >

    I had the exact same problem showing in the output of latencytest, and
    enabling unmaskirq on the drive being stressed solved it, thanks !

    See this for the problem :
    http://www.undata.org/~thomas/unmaskirq_0/index.html
    and this for the (impressive) results :
    http://www.undata.org/~thomas/unmaskirq_1/index.html

    Thomas


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