Hi, I was analyzing the code and behaviour of cpufrequtils (kernel 3.13). I noticed that the value reported by cpufreq-info as the frequency "asserted by call to hardware" (exported to sysfs as "cpuinfo_cur_freq") is always the same as the value reported as the frequency requested by a governor (exported to sysfs as "freq", stored in policy->cur). It was not the case for kernel 3.2 (these two values tend to differ). I found a reason: while using acpi-cpufreq driver, the value reported as hardware frequency is retrieved using get_cur_freq_on_cpu function (defined in acpi-cpufreq). Now, in kernel version 3.2 this function reads a value from MSR_IA32_PERF_STATUS, while in kernel 3.13 it reads MSR_IA32_PERF_CTL. It is a result of the patch shown below: https://lists.ubuntu.com/archives/kernel-team/2013-June/029493.html It looks like a bug for me - we take a requested frequency (control register) and we report it as "cpuinfo_cur_freq - Current frequency of the CPU as obtained from the hardware, in KHz. This is the frequency the CPU actually runs at." (as desribed in cpufrequtils documentation: https://www.kernel.org/doc/Documentation/cpu-freq/user-guide.txt";. I believe we should read status register (MSR_IA32_PERF_STATUS) instead. Best regards, Magdalena Dobosz -- To unsubscribe from this list: send the line "unsubscribe cpufreq" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
