Re: [patch] voluntary-preempt-2.6.9-rc1-bk4-R1

[Thomas Charbonnel]

Alan Cox wrote :
> On Mer, 2004-09-08 at 21:33, Mark_H_Johnson@xxxxxxxxxxxx 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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