Re: [PATCH v2] perf metrics: Add literal for system TSC frequency

Ian Rogers
2022-05-28T14:50:58Z

On Sat, May 28, 2022 at 7:02 AM Peter Zijlstra <peterz@infradead.org> wrote:
>
> On Fri, May 27, 2022 at 07:54:19AM -0700, Andi Kleen wrote:
>
> > > This all seems bonghits inspired... and perf actually does expose the
> > > tsc frequency. What do you think is in perf_event_mmap_page::time_* ?
> >
> >
> > That's not really available to perf stat, which is the primary metrics user.
>
> Why not? You can mmap any perf-fd (even software events) and these
> fields should be filled out.
>
> It should work on any x86 CPU that has a TSC. The only caveat is that
> the kernel must not have marked the TSC unstable.
>
> It could even work for virt -- all you need is for virt to use
> native_sched_clock() instead of the paravirt nonsense.

It will at least fail if inherit is enabled, no?

Thanks,
Ian