How to use ACPI CPUfreq driver in Red Hat Enterprise Linux 7 ?

Solution Verified - Updated -

Environment

  • Red Hat Enterprise Linux 7.x

Issue

Getting below errors while loading ACPI CPUfreq driver

# modprobe acpi_freq
modprobe: FATAL: Module acpi_freq not found. 

# modprobe acpi-cpufreq
FATAL: Error inserting acpi_cpufreq (/lib/modules/2.6.32-220.13.1.el6.x86_64/kernel/arch/x86/kernel/cpu/cpufreq/acpi-cpufreq.ko): No such device

In some cases observing below messages on bootup :

kernel: p4-clockmod: Warning: EST-capable CPU detected. The acpi-cpufreq
module offers voltage scaling in addition of frequency scaling. You 
should use that instead of p4-clockmod, if possible.

Resolution

  • First ensure that the system BIOS is configured to allow the OS to control CPU power management.

Ex : Follow below ways in case of HP ProLiant DL380 Gen10 Hardware

System configuration ---> Bios ---> Power Management and then changed 'Power Profile' to custom and Power Regulator to 'OS Control Mode'
alt text

Note: Above ways will be different in case of different hardware,the main objective is just to switch control of Power Management to OS.

  • Second add intel_pstate=disable as kernel command line parameter
GRUB_CMDLINE_LINUX="crashkernel=auto rd.lvm.lv=rhel_hp/root rd.lvm.lv=rhel_hp/swap intel_pstate=disable  console=ttyS0,115200"

Refer How do I permanently modify the kernel command line in RHEL7?

Verify the presence of intel_pstate=disable parameter within the /proc/cmdline file:

# grep intel_pstate /proc/cmdline

Diagnostic Steps

  • Following CPUfreq modules are available
$ ls /lib/modules/<kernel-version>/kernel/drivers/cpufreq
acpi-cpufreq.ko.xz  amd_freq_sensitivity.ko.xz  cpufreq_stats.ko.xz  p4-clockmod.ko.xz  pcc-cpufreq.ko.xz  powernow-k8.ko.xz  speedstep-lib.ko.xz
  • Initially following outputs displayed
$ cpupower frequency-info 
analyzing CPU 0:
  no or unknown cpufreq driver is active on this CPU  <<------ 
  CPUs which run at the same hardware frequency: Not Available
  CPUs which need to have their frequency coordinated by software: Not Available
  maximum transition latency:  Cannot determine or is not supported.
  hardware limits: Not Available
[..........]

$ 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: 1.20 GHz - 2.40 GHz
  available cpufreq governors: conservative userspace powersave ondemand performance
  current policy: frequency should be within 1.20 GHz and 2.40 GHz.
                  The governor "performance" may decide which speed to use
[..................]

After following Resolution we can confirm from below command output that ACPI CPUfreq module loaded

$ 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 - 2.40 GHz
  available frequency steps:  2.40 GHz, 2.40 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 2.40 GHz.
                  The governor "performance" may decide which speed to use
[........]

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