>
> > + if (sample->read.time_running > 0) {
> > + freq.tsc_freq = (1000 * sample->tsc) / sample-
> >read.time_running;
> > + freq.avg_freq = (1000 * sample->aperf) / sample-
> >read.time_running;
> > + if (sample->aperf > 0)
> > + freq.bzy_freq = freq.tsc_freq * sample->mperf /
> sample->aperf;
>
> Sorry didn't notice that earlier. The formula is not correct.
> aperf/mperf is not necessarily the frequency, it is essentially a load
> average of the CPU. It should be reported as such. Also only the ratio is
> architecturally defined.
>
The concept of tsc, avg and bzy are from turbostat.
Here is the definition from turbostat readme.
- AVG_MHz = APERF_delta/measurement_interval. This is the actual
number of elapsed cycles divided by the entire sample interval
- TSC_MHz = TSC_delta/measurement_interval.
On a system with an invariant TSC, this value will be constant
and will closely match the base frequency value
- Bzy_MHz = TSC_delta/APERF_delta/MPERF_delta/measurement_interval
Only the Bzy_MHz is wrong and has a typo error.
Other formula should be correct.
If it's confusion, I will change the name and make it consistent as turbostat.
> The right way to compute frequency is cycles / ref-cycles TSC can be used
> to accurately compute CPU utilization tsc / ref-cycles
I think I can add the support for frequency and CPU% calculation,
and show them in --stdio.
Thanks,
Kan
>
> It would be useful to report all three metrics.
>
> -Andi
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