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DateMon, 06 Sep 2004 22:17:22 -0500
From"K.R. Foley" <>
SubjectRe: [patch] voluntary-preempt-2.6.9-rc1-bk12-R5
Lee Revell wrote:
> On Mon, 2004-09-06 at 02:30, Ingo Molnar wrote:
>
>>* Lee Revell <rlrevell@joe-job.com> 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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