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I'm a cpufrequtils newbie. In the years I've been running Arch on my laptop, I've never set it up.
I wonder, why should I care about cpufrequtils? What should I know about the technology as a laptop user? Does the fact that I rarely unplug make a difference?
I also wonder what module I should be using for frequency scaling. The cpufrequtils article recommends acpi-cpufreq, but the article for my specific laptop recommends p4_clockmod (for some unspecified reason).
Any insight would be greatly appreciated. Thanks in advance!
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Just modprobe both acpi-cpufreq and p4-clockmod, only one of them should be able to load.
For older Intel CPUs, the command above may return with:
FATAL: Error inserting acpi_cpufreq ([...]/acpi-cpufreq.ko): No such device
In this case, replace the kernel module acpi-cpufreq with speedstep-centrino, p4-clockmod or speedstep-ich.
CPU frequency scaling saves power and keeps your processor cooler. It's worth using on a desktop or a server, not just a laptop.
If you use the ondemand governor, and add:
(sleep 5 && echo 11 > /sys/devices/system/cpu/cpufreq/ondemand/up_threshold)to /etc/rc.local, you'll have basically zero performance loss. Usually it scales up the CPU at 95%, with this it will do it at 11% (you can't go lower atm).
You can load the "cpufreq_stats" module and see what it's doing with cpufreq-info. You should notice your laptop fan spin down quite a bit once you set it up.
If you have a watt meter, you can take out the battery and see the power use drop from something like 17w to 12w.
Last edited by thestinger (2010-11-26 05:18:31)
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Very, very interesting. Thanks for the info.
I hope to have laptop-mode-tools manage scaling as the article suggests, but I'll definitely keep your suggestion regarding the ondemand governor in mind and bookmarked.
Thanks for the info. Enjoy Toronto (I always liked it there).
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