CPU Frequency Stability Issue

Background Information
During the CPU stress testing of the server in the environment with CentOS 7.9 and kernel version 5.15.13, it was found that the CPU frequency could not be maintained at a high frequency. Therefore, a CPU frequency stress test was conducted on the server. The following information provides a detailed description of the relevant test conditions. Please refer to it:

Test Environment
Different system versions + the same kernel version:
CentOS 7.9 + Kernel 5.15.13-1.el7
RedHat 9.1 + Kernel 5.15.13-1.el7

Test Plan 1
RHEL 9.1 system image + 5.15.13 kernel
Set BIOS system profile to performance mode
Run cpupower idle-set -D 0
After several hours of observation, the CPU frequency can remain stable at a high frequency.

Test Plan 2
CentOS 7.9 system image + 5.15.13 kernel
Set BIOS system profile to performance mode
Run cpupower idle-set -D 0
After several hours of observation, the CPU frequency cannot remain stable at a high frequency.

Test Plan 3
CentOS 7.9 system image + 6.8.9 kernel
Set BIOS system profile to performance mode
Run cpupower idle-set -D 0
After several hours of observation, the CPU frequency can remain stable at a high frequency.

Test Result Questions
With the same kernel version, the system version RHEL 9.1 can keep the CPU frequency running at a high frequency, while the system version CentOS 7.9 cannot keep the CPU frequency stable. Does RHEL 9.1 have special settings for the CPU frequency? What are these settings?
The CPU frequency test was performed on the server with system version CentOS 7.9 + kernel version 6.8.9, and it can keep the CPU frequency stable at a high frequency. Does this indicate that the kernel 6.8.9 has made fixes or restrictions for CPU frequency stability? Where are these fixes or restrictions set?

If it’s Intel I might suspect something related to the different cpuidle methods between kernels. Intel has their own idle with different methods, but there’s also a generic ACPI one. Then there’s differences with the halt and mwait(?) methods too.

I also heard there was a known performance issue with some kind of idle method when hyperthreading and/or C-States was enabled.

From Ask Fedora to CentOS

Added centos and removed kernel, server