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#1 2012-01-09 14:26:56

kleskjr
Member
Registered: 2011-12-31
Posts: 34

CPU locks to the lowest frequency

Hi,

I have an annoying issue with my laptop (Thinkad t410, i5-540): Under heavy use the cpu locks to the lowest 1200MHz and I can't do nothing to increase it back. When I run very demanding simulations (one-core load), usually in the first 5 minutes it performs perfectly and then the performance drops. Also I don't think it is a temperature issue, because the temperature hardly gets up to 70,80 degrees (C).

cpu-freq has no control here.

Here is part of the cpu-info output:

  driver: acpi-cpufreq
  CPUs which run at the same hardware frequency: 0 1 2 3
  CPUs which need to have their frequency coordinated by software: 3
  maximum transition latency: 10.0 us.
  hardware limits: 1.20 GHz - 2.53 GHz
  available frequency steps: 2.53 GHz, 2.53 GHz, 2.40 GHz, 2.27 GHz, 2.13 GHz, 2.00 GHz, 1.87 GHz, 1.73 GHz, 1.60 GHz, 1.47 GHz, 1.33 GHz, 1.20 GHz
  available cpufreq governors: ondemand, performance
 [b] current policy: frequency should be within 1.20 GHz and 1.20 GHz. [/b]
                  The governor "ondemand" may decide which speed to use
                  within this range.
  current CPU frequency is 1.20 GHz.

According to Thinkwiki, this happens in case I am using 65W adapter without a battery, but currently I using 95W (no battery). I also tried to disable the BIOS cpu limit by adding 'processor.ignore_ppc=1' in the boot menu list, without success. Additionally, the power setting in BIOS is set to performance.

Do you have any suggestions how can I take control over the CPU frequency?

thanks,
kleskjr

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#2 2012-01-09 19:41:18

olive
Member
From: Belgium
Registered: 2008-06-22
Posts: 1,490

Re: CPU locks to the lowest frequency

Look at the files in /sys/devices/system/cpu/cpu0/cpufreq. The actual scheme is in scaling_governor. Be sure to have the performance governor  and do

 echo "performance" > scaling_governor 

. If all what you want is to have always full performance, then just blacklist acpi-cpufreq in /etc/modprobe.d/modprobe.conf and reboot. Some packages may provide daemon that control the cpu frequencies; these daemon monitor various things and use the file in the above directories. More information can be found in the wiki: https://wiki.archlinux.org/index.php/CP … cy_Scaling

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#3 2012-01-10 09:15:26

kleskjr
Member
Registered: 2011-12-31
Posts: 34

Re: CPU locks to the lowest frequency

Problem solved! There is a BIOS option: Adaptive Thermal Management which was set to balance. Seems that under this condition, when the laptop gets too hot, instead of increasing the fan speed (and the noise), the BIOS just locks the CPU at lowest speed. Now it is set to performance and everything is normal.
@olive, thanks. Unfortunately CPU scaling doesn't have any influence once the CPU is locked down.

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