How to get real CPU frequency while system running?

Question

Because of the Intel Turbo Boost technology, I can't trust the CPU frequency written on the chip. I want to get the real CPU frequency while system running. I searched that cpufreq device could help. But dev.cpu.n.freq turned out only support for dev.cpu.0.freq.

There are no other OID like dev.cpu.1.freq or dev.cpu.n.freq.

Is there any useful tool could see the CPU frequency immediately?

Answer 1

Regarding the absence of the dev.cpu.N.freq sysctl for N>0, look at the BUGS section of cpufreq(4):

When multiple CPUs offer frequency control, they cannot be set to differ‐ ent levels and must all offer the same frequency settings.

This is why only CPU 0 is reported.