turboboost

Intel Turbo Boost is a feature that automatically raises CPU operating frequency when demanding tasks are running. It can be permanently disabled in BIOS. Check FAQ for more information. To disable turbo in Linux do:

# Intel
echo 1 > /sys/devices/system/cpu/intel_pstate/no_turbo
# AMD
echo 0 > /sys/devices/system/cpu/cpufreq/boost

Also you might want to take a look at how it’s done in uarch-bench.

Example (single-threaded workload running on Intel® Core™ i5-8259U):

# TurboBoost enabled
$ cat /sys/devices/system/cpu/intel_pstate/no_turbo
0
$ perf stat -e task-clock,cycles -- ./a.out
      11984.691958      task-clock (msec)         #    1.000 CPUs utilized
    32,427,294,227      cycles                    #    2.706 GHz
      11.989164338 seconds time elapsed
# TurboBoost disabled
$ echo 1 | sudo tee /sys/devices/system/cpu/intel_pstate/no_turbo
1
$ perf stat -e task-clock,cycles -- ./a.out
      13055.200832      task-clock (msec)         #    0.993 CPUs utilized
    29,946,969,255      cycles                    #    2.294 GHz
      13.142983989 seconds time elapsed

You can see the average frequency is much higher when TurboBoost is on.

Ref

https://easyperf.net/blog/2019/08/02/Perf-measurement-environment-on-Linux