Hi, So, currently there seems to be 3 issues in this thread (and I am guessing a little, without definitive data): 1.) On your system Kernel 5.4-rc2 (or 4) defaults to the intel_pstate CPU frequency scaling driver and the powersave governor, but kernel 4.6 defaults to the acpi-cpufreq CPU frequency scaling driver and the ondemand governor. Suggest to check the related kernel configuration parameters. $ grep -A 10 -i "CPU frequency scaling drivers" .config # CPU frequency scaling drivers # CONFIG_X86_INTEL_PSTATE=y CONFIG_X86_PCC_CPUFREQ=y CONFIG_X86_ACPI_CPUFREQ=y CONFIG_X86_ACPI_CPUFREQ_CPB=y CONFIG_X86_POWERNOW_K8=y CONFIG_X86_AMD_FREQ_SENSITIVITY=m CONFIG_X86_SPEEDSTEP_CENTRINO=y CONFIG_X86_P4_CLOCKMOD=m 2.) With kernel 5.2-rc2 there is thermal throttling (thermald?), but for Kernel 4.6 it either doesn't hit the throttling threshold or is not enabled. I don't have input here. However note that the CPU frequency verses load graphs are quite different between acpi-cpufreq/ondemand and intel-pstate/powersave, with higher CPU frequencies at lower loads for the acpi-cpufreq driver and higher CPU frequencies at higher loads for the intel_pstate driver. The crossover point is about 35% load. So, the two driver/governors might well end up at different operating pointing terms of CPU frequencies. I do not have energy data for the CPU frequency verses load tests, which is really what matters. 3.) The older kernel is still using the older acpi-cpufreq stuff where some CPU frequency memory registers show what was asked for and not what the system is actually giving. See below. On 2019.06.09 04:18 Pavel Machek wrote: > When I start flightgear, I get framerates around 20 fps and cpu at > 3GHz: > > pavel@duo:~/bt$ cat /proc/cpuinfo | grep MHz > cpu MHz : 3027.471 > cpu MHz : 2981.863 > cpu MHz : 2958.352 > cpu MHz : 2864.001 > pavel@duo:~/bt$ > > (Ok, fgfs is really only running at single core, so why do both cores > run at 3GHz?) There is only 1 PLL (Phase Locked Loop) master clock generator in your processor. Basically, the CPU with the highest frequency demand wins. What is not shown in your data is that the not busy core is also probably in a deep idle state for most of the time, consuming little or no energy. Below is an example from my processor (i7-2600K) using turbostat (note C6 is my deepest idle state, and only it is shown for simplicity): Core CPU Busy% Bzy_MHz CPU%c6 PkgTmp PkgWatt - - 12.52 3799 74.88 54 23.87 0 0 0.05 3664 99.89 54 23.87 0 4 0.00 3695 1 1 0.07 3676 99.87 1 5 0.00 3667 2 2 0.09 3669 99.78 2 6 0.00 3666 3 3 0.04 3786 0.00 3 7 99.92 3800 Observe the busy core spending no time in C6, but the other 3 spend most of the time there. However, for the little time that they are active, CPU 7 is the one demanding the high CPU frequency. Anticipated question: "Then why aren't all the CPU frequencies exactly the same?" My processor's max turbo frequency is a function of how many cores are active, and so actually varies under peak demand. Excerpt from turbostat, not in quiet mode: 35 * 100.0 = 3500.0 MHz max turbo 4 active cores 36 * 100.0 = 3600.0 MHz max turbo 3 active cores 37 * 100.0 = 3700.0 MHz max turbo 2 active cores 38 * 100.0 = 3800.0 MHz max turbo 1 active cores > The CPU is Intel(R) Core(TM) i5-2520M CPU @ 2.50GHz . I guess it means > it should be able to sustain both cores running at 2.5GHz? No, that is more a function of your hardware's ability (or lack of) to move the waste heat away. > Situation is very different with v4.6 distro based kernel. > > CPU MHz is only getting values round to 100MHz. It does not go above > 2.5GHz, but it does not go below 2.5GHz under the load, either. Yes, it is going above 2.5 GHz, see below. > v4.6: > cpu MHz : 2501.000 > cpu MHz : 2501.000 > cpu MHz : 2501.000 > cpu MHz : 2501.000 That seems to be the old acpi-cpufreq information, which is telling you what it's asking for and not what it actually is. And the "01" means it is asking for turbo range frequencies. Example from my system, while running the above CPU 7 busy test: Conditions: Old kernel (4.4), acpi-cpufreq driver, ondemand gov. doug@s15:~$ grep MHz /proc/cpuinfo cpu MHz : 1600.000 cpu MHz : 1600.000 cpu MHz : 1600.000 cpu MHz : 1600.000 cpu MHz : 1600.000 cpu MHz : 1600.000 cpu MHz : 1600.000 cpu MHz : 3401.000 CPUs 0-6 have very little load and are asking for the minimum available frequency. CPU 7 is asking for turbo. The turbostat data tells a different story. Conditions: New kernel (5.2-rc3), acpi-cpufreq driver, ondemand gov. doug@s15:~$ grep MHz /proc/cpuinfo cpu MHz : 3611.623 cpu MHz : 3638.843 cpu MHz : 3662.703 cpu MHz : 3634.156 cpu MHz : 3611.601 cpu MHz : 3668.422 cpu MHz : 3611.471 cpu MHz : 3738.445 Conditions: New kernel (5.2-rc3), intel_pstate driver, powersave gov. doug@s15:~$ grep MHz /proc/cpuinfo cpu MHz : 3651.506 cpu MHz : 3643.422 cpu MHz : 3611.678 cpu MHz : 3674.237 cpu MHz : 3612.469 cpu MHz : 3670.185 cpu MHz : 3612.050 cpu MHz : 3727.283 turbosat (tools/power/x86/turbostat/turbostat.c) commands used above: sudo turbostat --quiet --hide IRQ,Avg_MHz,SMI,\ GFXMHz,TSC_MHz,GFXWatt,CorWatt,POLL%,CPU%c1,\ CPU%c3,CPU%c7,CoreTmp,GFX%rc6,Pkg%pc2,Pkg%pc3,\ Pkg%pc6,POLL,C1,C1E,C3,C6,C1%,C1E%,C3%,C6% \ --interval 5 And: sudo turbostat ... Doug
