powerd adaptive mode latching

Daniel O'Connor doconnor at gsoft.com.au
Wed Jan 16 17:04:06 PST 2008

On Sun, 13 Jan 2008, Maxim Sobolev wrote:
> I wonder if somebody did measurement of power consumption with powerd
> and without it on typical tasks. There is very interesting idea in
> the last issue of ACM Queue that it might be much more beneficial to
> run CPU at the full speed and then switch it to low-power mode as
> soon as possible in the idle loop than to run longer at reduced speed
> for a longer period of time.

I did a bit of testing on a road trip once using acipconf -i 0 to 
measure current draw.

One problem with it is that it lags behind actual usage by a few seconds 
(presumably averaging it).

Still, at full steam (md5'ing /dev/zero at 1.4GHz) my laptop uses ~34W 
vs ~20W idle (which is ~300MHz depending on what KDE is doing :).

Turning the LCD off saves about 4W too.

I set my powerd flags like so..
powerd_flags="-i 70 -r 30 -a adaptive -b adaptive -n adaptive -p 200"

Daniel O'Connor software and network engineer
for Genesis Software - http://www.gsoft.com.au
"The nice thing about standards is that there
are so many of them to choose from."
  -- Andrew Tanenbaum
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