The cpu_khz and tsc_khz are now read directly by the cpuid instruction, and they are deemed to be very accurate. But this is not the case in our situation. The OS time lags behind about 8 seconds per hour. The CPU information is as follows: processor : 0 vendor_id : GenuineIntel cpu family : 6 model : 85 model name : Intel(R) Xeon(R) Gold 6140 CPU @ 2.30GHz stepping : 4 microcode : 0x200004d cpu MHz : 2300.000 cache size : 25344 KB physical id : 0 siblings : 36 core id : 0 cpu cores : 18 apicid : 0 initial apicid : 0 fpu : yes fpu_exception : yes cpuid level : 22 It is this "cpuid level 22" that makes the kernel 4.14 to read both cpu_khz and tsc_khz directly by instruction "cpuid", and the TSC is thought to be very accurate, but in fact it is not. ------------ * TSC frequency determined by CPUID is a "hardware reported" * frequency and is the most accurate one so far we have. This * is considered a known frequency. +* +* The assumption may not be valid! +* */ - setup_force_cpu_cap(X86_FEATURE_TSC_KNOWN_FREQ);
