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Buffoon
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PostPosted: Thu Jun 23, 2016 6:22 pm    Post subject: Intel CPU Power Management Reply with quote

So I enabled Intel P-State driver in kernel along with performance and powersave governors. After reading this. Now conky is showing 3.7 GHz at all times. I wonder what is really going on, is my CPU power and frequency managed properly or not? It is sixth gen i3.
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Logicien
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PostPosted: Thu Jun 23, 2016 6:34 pm    Post subject: Reply with quote

At boot, the kernel use the default governor as it is configure. It will not change governor by itself. You need utilities like cpufrequtils and cpupower to change the governor as a boot service. Some utilities can change the governor on the fly depending on several criterias. Othewise, the kernel stay using the default governor.

I don't know Conky but, if it can change the govervor, the appropriate modules must be load to do so if not in the kernel image itself.
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Buffoon
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PostPosted: Thu Jun 23, 2016 6:50 pm    Post subject: Reply with quote

Thanks, but frankly, I do not think this is how P-States driver works. What you describe is older ACPI implementation.
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Roman_Gruber
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PostPosted: Thu Jun 23, 2016 7:48 pm    Post subject: Reply with quote

I use the tool called i7z to check the cpu states and frequency / turbo in use.

+ htop / top

the intel data sheet of your cpu will reveal the supported features of the cpu.

e.g. for myself: http://ark.intel.com/products/64899/Intel-Core-i7-3610QM-Processor-6M-Cache-up-to-3_30-GHz

--

Code:
cpupower frequency-set -g powersave
Setting cpu: 0
Setting cpu: 1
Setting cpu: 2
Setting cpu: 3
Setting cpu: 4
Setting cpu: 5
Setting cpu: 6
Setting cpu: 7
ASUS-G75VW roman #


powersave or performance ... there may be other options though.
or

-f frequency
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Ant P.
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PostPosted: Thu Jun 23, 2016 8:00 pm    Post subject: Reply with quote

With this driver the cpuidle numbers are more meaningful than cpufreq ones. powertop or cpupower will show you if it's working or not.
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Buffoon
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PostPosted: Thu Jun 23, 2016 8:09 pm    Post subject: Reply with quote

So what you make out of this output? I understand the CPU should manage itself in most part? True?
Code:
~ # cpupower frequency-info
analyzing CPU 0:
  driver: intel_pstate
  CPUs which run at the same hardware frequency: 0
  CPUs which need to have their frequency coordinated by software: 0
  maximum transition latency:  Cannot determine or is not supported.
  hardware limits: 800 MHz - 3.70 GHz
  available cpufreq governors: performance powersave
  current policy: frequency should be within 800 MHz and 3.70 GHz.
                  The governor "performance" may decide which speed to use
                  within this range.
  current CPU frequency: 3.70 GHz (asserted by call to hardware)
  boost state support:
    Supported: no
    Active: no
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Roman_Gruber
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PostPosted: Thu Jun 23, 2016 8:12 pm    Post subject: Reply with quote

I have an ivybridge i7-3610qm cpu.

Maybe you should try driver: acpi-cpufreq + MAy i kindly ask you to try out i7z package please?

Code:
cpupower frequency-info
analyzing CPU 0:
  driver: acpi-cpufreq
  CPUs which run at the same hardware frequency: 0
  CPUs which need to have their frequency coordinated by software: 0
  maximum transition latency: 10.0 us
  hardware limits: 1.20 GHz - 2.30 GHz
  available frequency steps:  2.30 GHz, 2.30 GHz, 2.20 GHz, 2.10 GHz, 2.00 GHz, 1.90 GHz, 1.80 GHz, 1.70 GHz, 1.60 GHz, 1.50 GHz, 1.40 GHz, 1.30 GHz, 1.20 GHz
  available cpufreq governors: conservative userspace powersave ondemand performance
  current policy: frequency should be within 1.20 GHz and 2.30 GHz.
                  The governor "powersave" may decide which speed to use
                  within this range.
  current CPU frequency: 1.20 GHz (asserted by call to hardware)
  boost state support:
    Supported: yes
    Active: yes
    3100 MHz max turbo 4 active cores
    3100 MHz max turbo 3 active cores
    3200 MHz max turbo 2 active cores
    3300 MHz max turbo 1 active cores
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Buffoon
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PostPosted: Thu Jun 23, 2016 8:26 pm    Post subject: Reply with quote

I will as soon as I get home. Thanks.

According to this I did everything right. It is just not working.
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Ant P.
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PostPosted: Thu Jun 23, 2016 8:35 pm    Post subject: Reply with quote

Buffoon wrote:
So what you make out of this output?

All looks correct. If you set it to powersave governor you should see it at 800MHz most of the time. `cpupower monitor` gives better details because it shows how much the hardware is powered down (i.e. various degrees of "0 MHz")
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Buffoon
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PostPosted: Thu Jun 23, 2016 8:36 pm    Post subject: Reply with quote

I'm confused. Probably need to sleep on it and try to wrap my head around it tomorrow with fresh caffeine.
Quote:
Understanding the cpufreq core governors and policies are important before
discussing more details about the Intel P-State driver. Based on what callbacks
a cpufreq driver provides to the cpufreq core, it can support two types of
drivers:
- with target_index() callback: In this mode, the drivers using cpufreq core
simply provide the minimum and maximum frequency limits and an additional
interface target_index() to set the current frequency. The cpufreq subsystem
has a number of scaling governors ("performance", "powersave", "ondemand",
etc.). Depending on which governor is in use, cpufreq core will call for
transitions to a specific frequency using target_index() callback.
- setpolicy() callback: In this mode, drivers do not provide target_index()
callback, so cpufreq core can't request a transition to a specific frequency.
The driver provides minimum and maximum frequency limits and callbacks to set a
policy. The policy in cpufreq sysfs is referred to as the "scaling governor".
The cpufreq core can request the driver to operate in any of the two policies:
"performance" and "powersave". The driver decides which frequency to use based
on the above policy selection considering minimum and maximum frequency limits.

The Intel P-State driver falls under the latter category, which implements the
setpolicy() callback. This driver decides what P-State to use based on the
requested policy from the cpufreq core. If the processor is capable of
selecting its next P-State internally, then the driver will offload this
responsibility to the processor (aka HWP: Hardware P-States). If not, the
driver implements algorithms to select the next P-State.

Since these policies are implemented in the driver, they are not same as the
cpufreq scaling governors implementation, even if they have the same name in
the cpufreq sysfs (scaling_governors). For example the "performance" policy is
similar to cpufreq’s "performance" governor, but "powersave" is completely
different than the cpufreq "powersave" governor. The strategy here is similar
to cpufreq "ondemand", where the requested P-State is related to the system load.
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