load and power management
Peter A
loony at loonybin.org
Tue Apr 13 23:51:02 UTC 2010
Hi,
I'm a bit confused on how power management and cpu load (should) work
together... I'm not talking about a busy cpu clocking higher and so on but
about how system usage is reported when the cpu frequency changes.
I run KDE and the CPU meter (systemloadviewer plasmoid) behaves very
erratically. One moment I have 50% load, then the next it drops down to 26%
only to go back up to 50% seconds later. When checking what is going on in the
system I noticed nothing unusual. I have most services disabled for security
reasons and run a pretty light desktop After a little digging I found that my
system usage barely seems to change - just enough to frequently push the CPU
one step up in clock frequency and then it drops back down almost immediately.
As soon as I fixed the clock frequency at the highest (cat scaling_max_freq >
scaling_min_freq) the cpu usage was reported as perfectly steady...
So - that leads me to a few questions:
Am I doing something wrong? My view is pretty simple but the few tests I did
seemed to all indicate the same thing...
How valuable is reporting the CPU usage if its not really shows how much of
maximum CPU power is used?
Wouldn't it make more sense to show CPU usage normalized to the maximum
frequency rather than the current frequency?
Does the load as display with uptime compensate for power management? I went
through some of the kernel code the scheduler and the cpufreq kernel modules
but didn't see anything.
Thanks,
Peter.
--
Censorship: noun, circa 1591. a: Relief of the burden of independent thinking.
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