Re: [PATCH v7 1/4] Create source symlink in perf object dir

[Andi Kleen <ak@linux.intel.com>]

On Thu, Jul 25, 2024 at 02:18:15AM -0700, Ian Rogers wrote:
> On Thu, Jul 25, 2024 at 12:28 AM Andi Kleen <ak@linux.intel.com> wrote:
> >
> > > > On some reflection your changes went into the wrong direction
> > > > because it ignored the (useful) single group property. Aggregation
> > > > on time really needs to be in perf report not here.
> > >
> > > Still don't understand this. You are sampling, that's why you use the
> > > period, how can both samples happen at the same time? Why can't
> >
> > It's leader sampling ({}:S) , so only one event samples and the others
> > in the group get collected/reset at the time the sample happens.
> > So all the events in the group measure the same time interval.
> 
> No, here is your test:
> 
> +       perf record -e '{cycles,instructions}' -o "${perfdatafile}"
> perf test -w noploop
> +       perf script -i "${perfdatafile}" -F +metric  > $scriptoutput

True. I don't think it affects the test functionality in this case, but it should
be using :S.

> 
> notice that you aren't using :S. You are grouping the events which has
> no meaning other than for multiplexing, which for 2 events you won't

Any use of {} means they are in the same group, so always contiguous in the
perf.data as the script metric code expects.

-Andi