Hyper mode for powerd

[Warren Block]

On Sun, 14 Jul 2013, Ian Smith wrote:

> What powerd(8) could really use is an update to its man page (or a page
> in the handbook, or wiki?) suggesting some reasonable defaults for the
> range of hardware nowadays running it.

Difficulty: finding "reasonable" defaults.  But given the values, I 
would be willing to add them to that page.

> I guess powerd(8) would be also a good place to mention the advantage of
> turning off p4tcc and acpi_throttle in loader.conf, as at least a step
> towards deprecating their use with powerd?  [Kevin, what do you think?]

Before that, there should probably be some benchmarks, both for 
performance and power usage.  Those last results I posted left both 
settings at the default (enabled).  I don't know if they do any harm 
that way.  Again, a power usage benchmark would be interesting.  A heat 
level benchmark ought to be possible with the built-in temperature 
sensors.

> > > Hunting away.
> >
> > Is that a bad thing, though?  Effectively, it's just PWM, if you see what I
> > mean.
>
> I do, but to extend that analogy, compare an inverter with squarewave
> output to one using a stepped pseudo-sine wave, as most non-pure-sine
> inverters do today, much smoother and more efficient too.  I don't know
> the actual cost of changing freqs via sysctl, but suspect less often and
> smaller stepsizes are going to be more efficient and less likely to
> shift to a wildly inappropriate freq for load.  Perhaps my mechanical
> engineering bent worries about wear and tear on the 'gearbox', as it
> were, which of course we know to be a non-issue electronically :)

I thought that was what Kevin was saying, that shifting to full idle or 
full throttle was the most efficient.  Even if there is a higher cost to 
larger frequency changes, it may be more than offset by power savings or 
processing capacity.

> > The same periodic daily test as before, again with the first run discarded to
> > load the cache.
> >
> > powerd -a hyper -n hyper -p 50 -v > /tmp/powerd.log
> > 977.44 real        47.79 user       238.48 sys
> >
> > powerd -a hadp -n hadp -p 50 -v > /tmp/powerd.log
> > 874.18 real        28.89 user       140.00 sys
>
> Well hadp here gets the job done more quickly at any rate, both
> absolutely and in terms of system and user time.

Possibly due to the slower throttling down when the system is detected 
to be idle.

> If you're really burning up to hack on powerd :) a timestamp including
> milliseconds on the -v output lines (which might be cut to two lines max
> per change) would make it far easier to see what was happening, when ..

This really has me thinking more about benchmarks now.