Assume we are running on the single-package X86 machine, how to answer the question: what is the possible maximum tsc frequency ?
I read tsc_levels_changed(), is it the right way to query the max frequency for the general purpose driver ? If yes, could the code be made into the utility function ? BTW, there is some usage of the barriers in sysctl_machdep_tsc_freq() that I do not understand. When the read from tsc_freq is performed with the acquire semantic ? Why there are two store barriers when tsc_freq and tsc_timecounter.tc_frequency are written ? I would think that a single barrier on the last write is enough, but is it needed at all ?
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