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eddietsaitalk
Adept I
‎12-13-2017 03:41 AM

Why did I get different idle CPU frequency behaviors in RHEL and Windows Server 2016 with the same EPYC system and BIOS settings? RHEL always had fixed frequency.

With the same system configuration and the same BIOS setting. (CPU: EPYC 7451) I would see CPU idle frequency was shown as 2.3GHz always in RHEL 7.4 and 1.2GHz in Windows server 2016.

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eddietsaitalk
Adept I
‎12-13-2017 03:54 AM

That's probably caused by different CPU frequency scaling setting in different OS. Use below steps/command to check and modify the scaling governor in Linux OS.

  • Checked the scaling_governor; to check if it’s set to performance mode.
    • cat /sys/devices/system/cpu/cpu0/cpufreq/scaling_governor
    • performance /* performance would be shown if it's set to performance; other modes are ondemand, powersave...etc */
  • Check the CPU frequency by using the command below, would see the frequency of CPU0 was kept at 2.3G with 2.3G sku EPYC
    • cat /proc/cpuinfo | grep MHz | more

    • cpu MHz  :2300.000
    • cpu MHz : 2300.000
  • Edit the scaling governor as below. (You can change it to either ondemand or powersave) You will see the frequency of cpu0 was down to 1.2Ghz.
    • vi /sys/devices/system/cpu/cpu0/cpufreq/scaling_governor /* Then to edit the governor from performance to powersave */
    • cat /sys/devices/system/cpu/cpu0/cpufreq/scaling_governor
    • powersave
    • cat /proc/cpuinfo | grep MHz | more
    • cpu MHz  : 1200.000
    • cpu MHz : 2300.000

View solution in original post

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eddietsaitalk
Adept I
‎12-13-2017 03:54 AM

That's probably caused by different CPU frequency scaling setting in different OS. Use below steps/command to check and modify the scaling governor in Linux OS.

  • Checked the scaling_governor; to check if it’s set to performance mode.
    • cat /sys/devices/system/cpu/cpu0/cpufreq/scaling_governor
    • performance /* performance would be shown if it's set to performance; other modes are ondemand, powersave...etc */
  • Check the CPU frequency by using the command below, would see the frequency of CPU0 was kept at 2.3G with 2.3G sku EPYC
    • cat /proc/cpuinfo | grep MHz | more

    • cpu MHz  :2300.000
    • cpu MHz : 2300.000
  • Edit the scaling governor as below. (You can change it to either ondemand or powersave) You will see the frequency of cpu0 was down to 1.2Ghz.
    • vi /sys/devices/system/cpu/cpu0/cpufreq/scaling_governor /* Then to edit the governor from performance to powersave */
    • cat /sys/devices/system/cpu/cpu0/cpufreq/scaling_governor
    • powersave
    • cat /proc/cpuinfo | grep MHz | more
    • cpu MHz  : 1200.000
    • cpu MHz : 2300.000
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