Sluggish performance with kernel 5.7 (and higher)¶
Symptoms: you have configured the powersave scaling governor for intel_pstate:
and tlp-stat -p displays
/sys/devices/system/cpu/cpu0/cpufreq/scaling_driver = intel_cpufreq /sys/devices/system/cpu/cpu0/cpufreq/scaling_governor = powersave /sys/devices/system/cpu/cpu0/cpufreq/scaling_available_governors = conservative ondemand userspace powersave performance schedutil
Cause: starting with kernel 5.7, the intel_pstate scaling driver selects “passive mode” aka intel_cpufreq for CPUs that do not support hardware-managed P-states (HWP), i.e. Intel Core i 5th gen. or older. The governor powersave provided by intel_cpufreq works differently than the one provided by intel_pstate and produces the sluggish behaviour.
Solution: use the default governor – should be schedutil - by commenting above configuration lines or configure it explictly:
For details refer to CPU_SCALING_GOVERNOR_ON_AC/BAT.
Frequency scaling settings do not get applied¶
Symptom: tlp-stat -p shows values that do not reflect configuration.
There are several possible causes:
Invalid frequency settings
Solution: tlp-stat -p tells the possible frequencies for your CPU. Example:
/sys/devices/system/cpu/cpu0/cpufreq/scaling_available_frequencies = 2400000 1600000 800000 [kHz]
No ondemand governor with intel_pstate
Symptom: tlp-stat -p displays
/sys/devices/system/cpu/cpu0/cpufreq/scaling_driver = intel_pstate /sys/devices/system/cpu/cpu0/cpufreq/scaling_governor = powersave
Works as designed: since kernel 3.9 the new scaling driver intel_pstate is available and enabled by default on Intel Sandy Bridge (or newer) hardware. intel_pstate supports the governors powersave (recommended default) and performance only, ondemand is not available.
tlp-stat -p shows ‘x86_energy_perf_policy: program for your kernel not installed.’¶
Depending on the distribution your mileage may vary:
Ubuntu: install the metapackage linux-tools-generic or linux-tools-generic-lts-* for HWE stack kernels, no package is available for mainline kernels.
Debian: install the package linux-cpupower.
Arch: install the package x86_energy_perf_policy.
Fedora: install the package kernel-tools.