Messages in this thread | | | From | Andy Lutomirski <> | Date | Mon, 10 Feb 2014 12:47:12 -0800 | Subject | What should cpuinfo_cur_freq mean? |
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There are least three choices for what the "current frequency" is:
1. The frequency that the cpufreq driver thinks it has requested. This shows up in scaling_cur_freq.
2. The frequency that is actually programmed into the CPU. This is what acpi_cpufreq's cpuinfo_cur_freq reports.
3. A measurement of the number of cycles per unit time that are currently or recently happening. This is what intel_pstate reports.
The fact that acpi-cpufreq and intel_pstate behave differently here is unfortunate. I have servers [1] with broken BIOS that occasionally screw up the requested P-state (i.e. MSR 0x199). With acpi_cpufreq loaded, I can at least tell that there's a problem by reading cpuinfo_cur_freq. With intel_pstate loaded, I get a rapidly fluctuating value that depends on Turbo's current mood.
Can we separate out these concepts into separate sysfs files?
[1] These are fully up-to-date, recent generation Dell servers.
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