Re: RFC: powerd Patch & proposed future changes

Hi,

Patrick Lamaiziere wrote:
>>> I would like an option to set the minimum allowed CPU speed, instead
>>> the use of the sysctl debug.cpufreq.lowest.
>> This is so that powerd doesn't take so long to spin up power in the
>> adaptive modes?
> 
> If the speed is too low, my machine is not very interactive here
> (running KDE and all...).

Have you tried disabling throttling (P4TCC)?  Add these to your loader.conf:

hint.p4tcc.0.disabled=1
hint.acpi_throttle.0.disabled=1

When you reboot you'll notice a lot of frequencies missing from 
dev.cpu.0.freq_levels.  The remaining ones are those affected by EIST only.

The difference?  EIST controls CPU frequency *and* voltage.  Throttling 
controls only frequency, and is much less effective at saving power 
(while being very effective at slowing your system down).  If you 
disable throttling and use just EIST, your system will be much more 
responsive at a very small power cost.

The power cost above can be made up by setting C-state to C2 or even C3.

If you're running FreeBSD 8, another way of saving a lot of power on a 
notebook is to power down USB devices.  Most notebooks' webcams and 
fingerprint readers are internally connected to the USB bus.

Alexander Motin did a lot of testing a while ago.  Take a look at this 
thread:

http://lists.freebsd.org/pipermail/freebsd-current/2009-May/006436.html


Regards,
Aragon