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Intel Broadwell-U P-State vs. ACPI CPUFreq Scaling Linux Performance

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  • Intel Broadwell-U P-State vs. ACPI CPUFreq Scaling Linux Performance

    Phoronix: Intel Broadwell-U P-State vs. ACPI CPUFreq Scaling Linux Performance

    As some extra Broadwell Linux performance numbers this morning, here's some brief test results for the Intel Core i7 5600U when testing the Intel P-State vs. ACPI CPUFreq frequency scaling drivers and the different scaling governors...

    http://www.phoronix.com/scan.php?pag...-U-P-State-CPU

  • #2
    P-State driver doesn't work for my 4770k. Atleast not correctly. It would not scale down the frequency to the minimal values when doing nothing. I could only see ~2GHz with spikes to max speed just having terminal opened. Thanks to that temps were always higher than they should be.

    CPUFreq solved all issues. Michael, can you make investigation in this regard?

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    • #3
      VT Extensions enabled?

      I hope the laptop has VT disabled (VT-d specifically). Otherwise, as my Haswell, you will *not* get proper idle states.

      In my case: i915.enable_fbc=1 i915.enable_rc6=1 intel_iommu=igfx_off with intel_pstate on I get proper idle states

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      • #4
        Originally posted by Tares View Post
        P-State driver doesn't work for my 4770k. Atleast not correctly. It would not scale down the frequency to the minimal values when doing nothing. I could only see ~2GHz with spikes to max speed just having terminal opened. Thanks to that temps were always higher than they should be.

        CPUFreq solved all issues. Michael, can you make investigation in this regard?
        Works fine for me.
        Kernel 3.19-rc6 with Intel p-state built-in, traditional acpi cpufreq disabled.
        Scales down to 800MHz when idle and up to 4400MHz (that's the value I set up in the UEFI for max turbo clock) when under heavy load.
        The mobo is ASUS Maximus VI Hero.

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        • #5
          So maybe Ubuntu 14.10 standard kernel doesn't like my i7-4770k with MSI Z87-GD65 mobo :/ Anyway, it's not a big issue as long as I have an alternative

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          • #6
            @Tares
            Code:
            printf 'ENABLE="true"\nGOVERNOR="powersave"\n' > /etc/default/cpufrequtils

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            • #7
              Why should I modify cpufrequtils config? They are working correctly. P-state driver is the one causing issues.

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              • #8
                Before you complain look at the code!!! pstate is not the problem!

                Comment


                • #9
                  Please improve color coding of result table!

                  Currently the tables show the best value in green and the worst one in red.

                  Please:
                  - if the difference between best and worst is less than 1%, do not highlight any
                  - show any result with 99,5% of the best result in green as well.
                  - show any result with no more than 100,5% of the worst result in red as well

                  Thanks

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                  • #10
                    The main difference is that you don't need a tool like i7z to see the real cpu frequency in case of turbo boost. With old code turbo boost only was shown in /proc/cpuinfo as +1 MHz.

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