[Coco] Kernel activity on the O-Scope

[Gene Heskett]

On Thursday 04 March 2010, Boisy G. Pitre wrote:
>I know posting attachments are discouraged, but in this case I hope folks
> don't mind.
>
>Working on my thesis here at school gives me the opportunity to play with
> some nice test equipment.  While doing some other measurements, I figured
> I would measure the percentage of the time NitrOS-9 runs when there is no
> process active.  Keep in mind that every 16.67ms the clock interrupt kicks
> in and the code in clock.asm checks interrupts, just to the kernel so it
> can do its housekeeping (checks the queues, etc.), then inserts the active
> process into the queue, or in this case, call the CWAI instruction since
> there is no active process.  The shell prompt was sitting there as I
> captured this.
>
> The graph below shows the amps in yellow, the volts in green and the LIC
> line in purple.   The little peaks represent the clock/kernel activity...
> the measured time is 700us, or .7ms.
>
>Doing the math,  .7/16.67 * 100= 4.2%.  So 4.2% of the clock period is
> spent in the kernel.
>
Most interesting Boisy.  My own SWAG's would have put it at less than 5%, 
based roughly on a snoop through the clock and associated stuff I did way 
back up the log when I restored the alarm & etc functions that had been 
stripped from later versions of the clock.  I assume in an effort to shrink 
it down the bare minimum.  But at the time that is all it was, a swag, no 
real instrumentation.  Looks as if I am confirmed for the most part, but it 
might be enlightening to see what its doing at the strike of midnight on new 
years when it has to chain completely through all the conditionals, 
incrementing and resetting as it goes.  That one instance might hit the 5% 
mark pretty solidly.

Curious, this was a 6809 machine, or a 6309 machine?  My guess is its a 6809 
since the currents actually look fairly stable.

-- 
Cheers, Gene
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