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alogim
Tux's lil' helper
Tux's lil' helper


Joined: 21 Aug 2015
Posts: 124

PostPosted: Fri Mar 29, 2019 4:41 pm    Post subject: Some advices with power management Reply with quote

As the title says I would like some help in configuring my laptop to let the battery last quite a lot. I am following this guide, however I have some questions.
First of all, how comes the suggested default CPU governor is performance? Shouldn't it be powersave instead?
I understand I am using Intel P-states so these are different from the traditional states, but still... having my CPU at 4.0 GHz certainly does not help battery life, especially when it could be down to 400 MHz.
Also, cpufreq is obsolete since kernel 2.6.x, but they say to configure things in /etc/laptop-mode/conf.d/cpufreq.conf. Is that a different thing?

If you can suggest some recommended settings, I would be very grateful.
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coolparadox
n00b
n00b


Joined: 28 May 2014
Posts: 8
Location: Brazil

PostPosted: Mon Jun 24, 2019 1:57 am    Post subject: Reply with quote

IIUC the CPUFreq governor should be off (ie, "performance" setting) because it would interfere with the P-states implementation that is embedded in your Intel CPU.

In my system I tune the CPU maximum performance by ultimately writing to intel_pstate runtime configuration files under /sys. For instance, to force the lowest CPU allowed performance:

Code:
cat /sys/devices/system/cpu/intel_pstate/min_perf_pct >/sys/devices/system/cpu/intel_pstate/max_perf_pct


And to revert back to full speed:

Code:
echo 100 >/sys/devices/system/cpu/intel_pstate/max_perf_pct


You may find useful to trigger such commands on e.g. ac_adapter ACPI events.

More details on intel_pstate files can be found at Documentation/admin-guide/pm/intel_pstate.rst of your Linux kernel sources.
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