More CPU Scaling Problems

Evan eapache at
Sun May 17 00:08:23 UTC 2009

1. What does Ubuntu use to scale CPU frequencies? Does it use the kernel
method, as described at [1], or something else?
2. Did the method change between Intrepid and Jaunty?

I ask these two questions because in Intrepid it worked fine out-of-the-box,
and in Jaunty it's been doing some really creepy things.

I originally started looking at this because the ignore_nice_load default
value (discussed previously) appeared to have changed. I wanted to change it
back, so as per the instructions at [1] I added the proper lines to my
/etc/rc.local file. The value was ignored, and I filed a bug regarding it at

I recently decided to change the default state of my cores from ondemand to
powersave, and since I saw no easier way to do it, I added another few lines
to rc.local. These also appeared to be ignored. Since I can change the
governor manually using the same cmd I added to rc.local, and I know
rc.local is being properly read, I knew something was fishy, so I did a few

This is what I determined: every few minutes, something changes the governor
on my CPU cores back to ondemand. I have a relatively vanilla install of
Jaunty 64, and I know I haven't installed anything extra that should be
touching my cpu governors (feel free to prove me wrong on this). Both the
gnome monitor applet and /sys/devices have been used to change the governor,
and both agree that it changes back. The ignore_nice_load value doesn't seem
to change, but the fact that it's being ignored seems like it's probably

Is something funny going on, or am I barking up the wrong tree?


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