On Wed, Aug 23, 2017 at 05:29:13PM -0500, R0b0t1 wrote:
> As an example, I am interested in characterizing the power consumption
> of rendering a PDF document. I would hopefully only need to run the
> renderer once.

I remember in college some interesting work in security-related stuff
that was about characterizing power draw in order to crack passwords.
Potentially that could be useful, as you could record the waveforms
going into your power supply while rendering a PDF, but it sure sounds
complicated.

> Apparently you can talk to these, but my searches can only find code
> which seems highly experimental. The other replies seem to be for
> embedded Linux systems running on FPGAs and perhaps Cortex-A parts.

Even if you could talk to these, taking periodic measurements of
current and voltage, then integrating over time would probably give
results with large errors.

> If I were using a microcontroller I could get uA or nA draw per MHz
> and I know my operating voltage and operating time. However, desktop
> processors are much more complex, and I am not sure if they have been
> entirely characterized. The most advanced tool I can find is PowerTOP
> and it does not seem very accurate.

Due to modern processors having things like pipelines and all of the
caching and memory pre-fetching going on behind the scenes, it's probably
not easy to measure this with any degree of accuracy.

Have fun,

Alec

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