Re: [RFC PATCH v5 1/6] perf stat: Parse and find tpebs events when parsing metrics to prepare for perf record sampling

[Namhyung Kim <namhyung@kernel.org>]

On Thu, Mar 28, 2024 at 11:43 PM Wang, Weilin <weilin.wang@intel.com> wrote:
>
>
>
> > -----Original Message-----
> > From: Namhyung Kim <namhyung@kernel.org>
> > Sent: Thursday, March 28, 2024 10:46 PM
> > To: Wang, Weilin <weilin.wang@intel.com>
> > Cc: Ian Rogers <irogers@google.com>; Arnaldo Carvalho de Melo
> > <acme@kernel.org>; Peter Zijlstra <peterz@infradead.org>; Ingo Molnar
> > <mingo@redhat.com>; Alexander Shishkin
> > <alexander.shishkin@linux.intel.com>; Jiri Olsa <jolsa@kernel.org>; Hunter,
> > Adrian <adrian.hunter@intel.com>; Kan Liang <kan.liang@linux.intel.com>;
> > linux-perf-users@vger.kernel.org; linux-kernel@vger.kernel.org; Taylor, Perry
> > <perry.taylor@intel.com>; Alt, Samantha <samantha.alt@intel.com>; Biggers,
> > Caleb <caleb.biggers@intel.com>
> > Subject: Re: [RFC PATCH v5 1/6] perf stat: Parse and find tpebs events when
> > parsing metrics to prepare for perf record sampling
> >
> > On Tue, Mar 26, 2024 at 1:29 PM <weilin.wang@intel.com> wrote:
> > >
> > > From: Weilin Wang <weilin.wang@intel.com>
> > >
> > > Metrics that use tpebs values would use the :retire_latency keyword in
> > > formulas. We put all these events into a list and pass the list to perf
> > > record to collect their retire latency value.
> > >
> > > Signed-off-by: Weilin Wang <weilin.wang@intel.com>
> > > Reviewed-by: Ian Rogers <irogers@google.com>
> > > ---
> > [SNIP]
> > > @@ -681,8 +685,56 @@ static int metricgroup__build_event_string(struct
> > strbuf *events,
> > >         hashmap__for_each_entry(ctx->ids, cur, bkt) {
> > >                 const char *sep, *rsep, *id = cur->pkey;
> > >                 enum perf_tool_event ev;
> > > +               /*
> > > +                * Parse and search for event name with retire_latency modifier.
> > > +                * If found, put event name into the tpebs_events list. This list
> > > +                * of events will be passed to perf record for sampling to get
> > > +                * their reitre_latency value.
> > > +                * Search for ":R" in event name without "@". Search for the
> > > +                * last "@R" in event name with "@".
> >
> > What is the retire_latency modifier exactly?
> > Why do you search for :R and @R?  What's the difference?
> > Why don't you search for "retire_latency"?
>
> We decided to use R as the modifier for retire_latency in one of the previous
> version of code review. Therefore, the code searches for R instead of "retire_latency".
>
> It should search for :R in usual cases. But in hybrid platform, event name might be in
> format like cpu_core@event_name@R.

Ok, thanks for the explanation.  Please update the commit message and
the comment with this info.

Thanks,
Namhyung