Re: [patch] voluntary-preempt-2.6.9-rc1-bk12-R5

[K.R. Foley]

Lee Revell wrote:
> On Mon, 2004-09-06 at 02:30, Ingo Molnar wrote:
>
> > * Lee Revell <rlrevell@xxxxxxxxxxx> wrote:
> >
> >
> > > http://krustophenia.net/testresults.php?dataset=2.6.9-rc1-R0#/var/www/2.6.9-rc1-R0/foo.hist
> > >
> > > I find the two smaller spikes to either side of the central spike
> > > really odd.  These showed up in my jackd tests too, I had attributed
> > > them to some measurement artifact, but they seem real.  Maybe a
> > > rounding bug, or some kind of weird cache effect?
> >
> > interesting - the histograms are pretty symmetric around the center.
> > E.g. the exponential foo.hist2 diagram is way too symmetric around 50
> > usecs! What precisely is being measured?
>
>
> Here's the program.  It does mlockall(), acquires realtime scheduling,
> then sets up a 2048 Hz stream of interupts from the RTC and measures the
> delay.  It's quite possible there's a bug, the amlat program did not
> seem to work, something must have changed with the RTC from 2.4 to 2.6.

Actually the amlat program works fine for applying real-time scheduling 
pressure. I believe it just doesn't do any real latency measuring 
without the hooks provided by Andrew's rtc-debug patch.

kr
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