Hardware Frequency Steps - Intel P-State vs ACPI CPUFREQ

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I have Intel Xeon Phi 7210 running CentOS 7 with kernel 3.10.0-514.el7.x86_64. I am comparing what frequency steps are available when I boot system into intel p-state vs when the system uses acpi cpufreq. I run sudo cpupower frequency-info to get following two logs.



Intel P-State



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: 1000 MHz - 1.50 GHz
available cpufreq governors: performance powersave
current policy: frequency should be within 1.40 GHz and 1.40 GHz.
The governor "performance" may decide which speed to use
within this range.
current CPU frequency: 1.30 GHz (asserted by call to hardware)
boost state support:
Supported: yes
Active: yes


ACPI CPUFREQ



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: 1000 MHz - 1.30 GHz
available frequency steps: 1.30 GHz, 1.30 GHz, 1.20 GHz, 1.10 GHz, 1000 MHz
available cpufreq governors: conservative userspace powersave ondemand performance
current policy: frequency should be within 1000 MHz and 1.30 GHz.
The governor "conservative" may decide which speed to use
within this range.
current CPU frequency: 1000 MHz (asserted by call to hardware)
boost state support:
Supported: yes
Active: yes


Why does two different scaling drivers show different hardware frequency limits? For intel p-state, I see frequency limits from 1GHz to 1.5GHz and on other hand acpi cpufreq shows 1GHz to 1.3GHz.



As per datasheet, the above processor can run at 1.5GHz with turbo boost, is that the reason why it's not available for acpi cpufreq?



Any specific reason why this is the case?



Thanks.







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    up vote
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    I have Intel Xeon Phi 7210 running CentOS 7 with kernel 3.10.0-514.el7.x86_64. I am comparing what frequency steps are available when I boot system into intel p-state vs when the system uses acpi cpufreq. I run sudo cpupower frequency-info to get following two logs.



    Intel P-State



    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: 1000 MHz - 1.50 GHz
    available cpufreq governors: performance powersave
    current policy: frequency should be within 1.40 GHz and 1.40 GHz.
    The governor "performance" may decide which speed to use
    within this range.
    current CPU frequency: 1.30 GHz (asserted by call to hardware)
    boost state support:
    Supported: yes
    Active: yes


    ACPI CPUFREQ



    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: 1000 MHz - 1.30 GHz
    available frequency steps: 1.30 GHz, 1.30 GHz, 1.20 GHz, 1.10 GHz, 1000 MHz
    available cpufreq governors: conservative userspace powersave ondemand performance
    current policy: frequency should be within 1000 MHz and 1.30 GHz.
    The governor "conservative" may decide which speed to use
    within this range.
    current CPU frequency: 1000 MHz (asserted by call to hardware)
    boost state support:
    Supported: yes
    Active: yes


    Why does two different scaling drivers show different hardware frequency limits? For intel p-state, I see frequency limits from 1GHz to 1.5GHz and on other hand acpi cpufreq shows 1GHz to 1.3GHz.



    As per datasheet, the above processor can run at 1.5GHz with turbo boost, is that the reason why it's not available for acpi cpufreq?



    Any specific reason why this is the case?



    Thanks.







    share|improve this question






















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      down vote

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      up vote
      1
      down vote

      favorite











      I have Intel Xeon Phi 7210 running CentOS 7 with kernel 3.10.0-514.el7.x86_64. I am comparing what frequency steps are available when I boot system into intel p-state vs when the system uses acpi cpufreq. I run sudo cpupower frequency-info to get following two logs.



      Intel P-State



      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: 1000 MHz - 1.50 GHz
      available cpufreq governors: performance powersave
      current policy: frequency should be within 1.40 GHz and 1.40 GHz.
      The governor "performance" may decide which speed to use
      within this range.
      current CPU frequency: 1.30 GHz (asserted by call to hardware)
      boost state support:
      Supported: yes
      Active: yes


      ACPI CPUFREQ



      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: 1000 MHz - 1.30 GHz
      available frequency steps: 1.30 GHz, 1.30 GHz, 1.20 GHz, 1.10 GHz, 1000 MHz
      available cpufreq governors: conservative userspace powersave ondemand performance
      current policy: frequency should be within 1000 MHz and 1.30 GHz.
      The governor "conservative" may decide which speed to use
      within this range.
      current CPU frequency: 1000 MHz (asserted by call to hardware)
      boost state support:
      Supported: yes
      Active: yes


      Why does two different scaling drivers show different hardware frequency limits? For intel p-state, I see frequency limits from 1GHz to 1.5GHz and on other hand acpi cpufreq shows 1GHz to 1.3GHz.



      As per datasheet, the above processor can run at 1.5GHz with turbo boost, is that the reason why it's not available for acpi cpufreq?



      Any specific reason why this is the case?



      Thanks.







      share|improve this question












      I have Intel Xeon Phi 7210 running CentOS 7 with kernel 3.10.0-514.el7.x86_64. I am comparing what frequency steps are available when I boot system into intel p-state vs when the system uses acpi cpufreq. I run sudo cpupower frequency-info to get following two logs.



      Intel P-State



      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: 1000 MHz - 1.50 GHz
      available cpufreq governors: performance powersave
      current policy: frequency should be within 1.40 GHz and 1.40 GHz.
      The governor "performance" may decide which speed to use
      within this range.
      current CPU frequency: 1.30 GHz (asserted by call to hardware)
      boost state support:
      Supported: yes
      Active: yes


      ACPI CPUFREQ



      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: 1000 MHz - 1.30 GHz
      available frequency steps: 1.30 GHz, 1.30 GHz, 1.20 GHz, 1.10 GHz, 1000 MHz
      available cpufreq governors: conservative userspace powersave ondemand performance
      current policy: frequency should be within 1000 MHz and 1.30 GHz.
      The governor "conservative" may decide which speed to use
      within this range.
      current CPU frequency: 1000 MHz (asserted by call to hardware)
      boost state support:
      Supported: yes
      Active: yes


      Why does two different scaling drivers show different hardware frequency limits? For intel p-state, I see frequency limits from 1GHz to 1.5GHz and on other hand acpi cpufreq shows 1GHz to 1.3GHz.



      As per datasheet, the above processor can run at 1.5GHz with turbo boost, is that the reason why it's not available for acpi cpufreq?



      Any specific reason why this is the case?



      Thanks.









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      asked Oct 28 '17 at 15:36









      Chetan Arvind Patil

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