It's not entirely predictable, though it may have something to do with actual use -- that is, maybe the kernel and/or the hardware is deciding that I'm running too hot and forceably underclocking me...
Here's what I currently see, when things are working:
Code:
> cpufreq-info
cpufrequtils 004: cpufreq-info (C) Dominik Brodowski 2004-2006
Report errors and bugs to cpufreq@lists.linux.org.uk, please.
analyzing CPU 0:
driver: acpi-cpufreq
CPUs which need to switch frequency at the same time: 0
hardware limits: 800 MHz - 2.50 GHz
available frequency steps: 2.50 GHz, 2.50 GHz, 2.00 GHz, 1.60 GHz, 1.20 GHz, 800 MHz
available cpufreq governors: conservative, ondemand, userspace, powersave, performance
current policy: frequency should be within 800 MHz and 2.50 GHz.
The governor "ondemand" may decide which speed to use
within this range.
current CPU frequency is 800 MHz.
cpufreq stats: 2.50 GHz:7.07%, 2.50 GHz:1.09%, 2.00 GHz:1.61%, 1.60 GHz:2.97%, 1.20 GHz:4.88%, 800 MHz:82.37% (190864)
analyzing CPU 1:
driver: acpi-cpufreq
CPUs which need to switch frequency at the same time: 1
hardware limits: 800 MHz - 2.50 GHz
available frequency steps: 2.50 GHz, 2.50 GHz, 2.00 GHz, 1.60 GHz, 1.20 GHz, 800 MHz
available cpufreq governors: conservative, ondemand, userspace, powersave, performance
current policy: frequency should be within 800 MHz and 2.50 GHz.
The governor "ondemand" may decide which speed to use
within this range.
current CPU frequency is 800 MHz.
cpufreq stats: 2.50 GHz:7.41%, 2.50 GHz:2.22%, 2.00 GHz:2.52%, 1.60 GHz:3.20%, 1.20 GHz:3.82%, 800 MHz:80.83% (192777)
The key line here is:
Code:
current policy: frequency should be within 800 MHz and 2.50 GHz.
The governor "ondemand" may decide which speed to use
within this range.
Note that the governor stays the same. When I ask this in IRC, most people immediately suggest making sure the governor is ondemand (it is), or making sure I'm plugged in (I am, but why should it matter?)
What happens is, the above changes to "frequency should be within 800 MHz and 800 MHz."
Changing this myself seems to have no effect, with:
Code:
sudo cpufreq-set -c 0 -u 2501Mhz
sudo cpufreq-set -c 1 -u 2501Mhz
Nine times out of ten, this returns success, but has absolutely no effect -- running cpufreq-info immediately afterwards shows I'm still at 800 MHz. It probably never has an effect, and I'm just seeing the system deciding that it's OK for me to run at full speed now.
I have no idea how long this has been happening, as the majority of my use doesn't require a particularly fast CPU. But when I need that power, I need that power, and it's getting frustrating.
System info: Kubuntu 9.04, Dell XPS M1530, /proc/cpuinfo reports Core2 Duo T9300 @ 2.50 GHz.
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