linux-kernel - Re: [PATCH 13/18] perf metric: Add events for the current group

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Date:   Wed, 15 Jul 2020 10:00:09 -0700
From:   Ian Rogers <irogers@...gle.com>
To:     Jiri Olsa <jolsa@...nel.org>
Cc:     Arnaldo Carvalho de Melo <acme@...nel.org>,
        lkml <linux-kernel@...r.kernel.org>,
        Ingo Molnar <mingo@...nel.org>,
        Namhyung Kim <namhyung@...nel.org>,
        Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
        Peter Zijlstra <a.p.zijlstra@...llo.nl>,
        Michael Petlan <mpetlan@...hat.com>,
        Andi Kleen <ak@...ux.intel.com>,
        Kajol Jain <kjain@...ux.ibm.com>,
        John Garry <john.garry@...wei.com>,
        "Paul A. Clarke" <pc@...ibm.com>,
        Stephane Eranian <eranian@...gle.com>
Subject: Re: [PATCH 13/18] perf metric: Add events for the current group

On Sun, Jul 12, 2020 at 6:27 AM Jiri Olsa <jolsa@...nel.org> wrote:
>
> There's no need to iterate the whole list of groups,
> when adding new events. The currently created group
> is the one we want to add.
>
> Signed-off-by: Jiri Olsa <jolsa@...nel.org>
> ---
>  tools/perf/util/metricgroup.c | 22 ++++++++++++----------
>  1 file changed, 12 insertions(+), 10 deletions(-)
>
> diff --git a/tools/perf/util/metricgroup.c b/tools/perf/util/metricgroup.c
> index 8cbcc5e05fef..66f25362702d 100644
> --- a/tools/perf/util/metricgroup.c
> +++ b/tools/perf/util/metricgroup.c
> @@ -811,17 +811,19 @@ static int metricgroup__add_metric(const char *metric, bool metric_no_group,

Could we add a function comment to describe the arguments here?
Currently events is an empty list out argument that is built up by
this code, now it will be incrementally updated. Except I don't think
I'm capturing the current state correctly, it is confusing that there
is the loop in the current code. It looks like events will be added
multiple times redundantly.

>         if (ret)
>                 return ret;
>
> -       list_for_each_entry(eg, group_list, nd) {
> -               if (events->len > 0)
> -                       strbuf_addf(events, ",");
> +       if (events->len > 0)
> +               strbuf_addf(events, ",");
>
> -               if (eg->has_constraint) {
> -                       metricgroup__add_metric_non_group(events,
> -                                                         &eg->pctx);
> -               } else {
> -                       metricgroup__add_metric_weak_group(events,
> -                                                          &eg->pctx);
> -               }
> +       /*
> +        * Even if we add multiple groups through the runtime
> +        * param, they share same events.
> +        */

I'm not clear what runtime param is here. Is it the \? arch runtime parameter?

Thanks,
Ian

> +       if (eg->has_constraint) {
> +               metricgroup__add_metric_non_group(events,
> +                                                 &eg->pctx);
> +       } else {
> +               metricgroup__add_metric_weak_group(events,
> +                                                  &eg->pctx);
>         }
>         return 0;
>  }
> --
> 2.25.4
>