[Tfug] "Normal" ondemand governor usage?

[Jeremy D Rogers]

Hi Claude,
You might just want to check that you are really using the ondemand
governor. I vaguely remember that some other governors used different time
scales to sclae up the cpu clock. So it wouldn't scale up unless you run
something that required more than half a second of cpu (eons to the proc).
Now that I think about it, that may have been the cpu "throttling" rather
than scaling which I think used a totally different interface. Someone who
remember can chime in here.

In any case, I would double check which governor is active with "cat
/sys/devices/system/cpu/cpu0/cpufreq/scaling_governor" (or equiv on your
platform) to make sure. That said, the lag you see could depend on what you
use to watch it. If you are relying on a monitor of some sort, there can be
a long delay and you might only see it bump to high speed after sustained
demand. You could try runnig some that demands some processing power like
compiling your kernel, or try watching it with something quicker like "watch
-n .1 cat /proc/cpuinfo" to see if it is actually responding quickly to
demand.
JDR
--
Jeremy D. Rogers, Ph.D.
Postdoctoral Fellow
Biomedical Engineering
Northwestern University


On Mon, Nov 24, 2008 at 3:23 PM, Claude Rubinson <rubinson at u.arizona.edu>wrote:

> I was just reviewing Matthew Garrett's "good practices" for power
> management (http://www.codon.org.uk/~mjg59/power/good_practices.html<http://www.codon.org.uk/%7Emjg59/power/good_practices.html>
> )
> and one of the things that he discusses is that one should use the
> ondemand power governor.  I do, but only very rarely does my cpu go
> above 600MHz (it's an Intel Pentium M that runs up to 1.2GHz).  For
> example, when starting up Firefox (Iceweasel), the cpu will briefly
> jump to 1200MHz and then return to 600.  Even when I run fairly
> intensive statistical analyses (RAM tends to be the bigger issue here)
> or watch video, the processor sticks to 600MHz.
>
> I've always just assumed this was because the processor simply wasn't
> being taxed but after reading Garrett's comments, I'm wondering if
> this is correct.  Should my processor be bursting more frequently?
> More to the point: How can I know if something's normal/buggy with my
> cpu frequency scaling?
>
> Thanks,
>
> Claude
>
> _______________________________________________
> Tucson Free Unix Group - tfug at tfug.org
> Subscription Options:
> http://www.tfug.org/mailman/listinfo/tfug_tfug.org
>
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://tfug.org/pipermail/tfug_tfug.org/attachments/20081124/5613516c/attachment-0002.html>