linux-kernel - Re: [PATCH v4] perf annotate: Fix sample events lost in stdio mode

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Date:   Sat, 13 Mar 2021 12:06:53 +0900
From:   Namhyung Kim <namhyung@...nel.org>
To:     Yang Jihong <yangjihong1@...wei.com>,
        Yao Jin <yao.jin@...ux.intel.com>
Cc:     Peter Zijlstra <peterz@...radead.org>,
        Ingo Molnar <mingo@...hat.com>,
        Arnaldo Carvalho de Melo <acme@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
        Jiri Olsa <jolsa@...hat.com>, gustavoars@...nel.org,
        mliska@...e.cz, linux-kernel <linux-kernel@...r.kernel.org>,
        zhangjinhao2@...wei.com
Subject: Re: [PATCH v4] perf annotate: Fix sample events lost in stdio mode

On Sat, Mar 13, 2021 at 11:16 AM Yang Jihong <yangjihong1@...wei.com> wrote:
>
> In hist__find_annotations function, since different hist_entry may point to same
> symbol, we free notes->src to signal already processed this symbol in stdio mode;
> when annotate, entry will skipped if notes->src is NULL to avoid repeated output.
>
> However, there is a problem, for example, run the following command:
>
>  # perf record -e branch-misses -e branch-instructions -a sleep 1
>
> perf.data file contains different types of sample event.
>
> If the same IP sample event exists in branch-misses and branch-instructions,
> this event uses the same symbol. When annotate branch-misses events, notes->src
> corresponding to this event is set to null, as a result, when annotate
> branch-instructions events, this event is skipped and no annotate is output.
>
> Solution of this patch is to remove zfree in hists__find_annotations and
> change sort order to "dso,symbol" to avoid duplicate output when different
> processes correspond to the same symbol.

Looks good.  But I'm not sure about the branch stack mode.
I suspect we can use the same sort key there.

Jin Yao, what do you think?

Thanks,
Namhyung

> ---
>  tools/perf/builtin-annotate.c | 13 ++++++-------
>  1 file changed, 6 insertions(+), 7 deletions(-)
>
> diff --git a/tools/perf/builtin-annotate.c b/tools/perf/builtin-annotate.c
> index a23ba6bb99b6..ad169e3e2e8f 100644
> --- a/tools/perf/builtin-annotate.c
> +++ b/tools/perf/builtin-annotate.c
> @@ -374,13 +374,6 @@ static void hists__find_annotations(struct hists *hists,
>                 } else {
>                         hist_entry__tty_annotate(he, evsel, ann);
>                         nd = rb_next(nd);
> -                       /*
> -                        * Since we have a hist_entry per IP for the same
> -                        * symbol, free he->ms.sym->src to signal we already
> -                        * processed this symbol.
> -                        */
> -                       zfree(&notes->src->cycles_hist);
> -                       zfree(&notes->src);
>                 }
>         }
>  }
> @@ -624,6 +617,12 @@ int cmd_annotate(int argc, const char **argv)
>                 if (setup_sorting(annotate.session->evlist) < 0)
>                         usage_with_options(annotate_usage, options);
>         } else {
> +               /*
> +                * Events of different processes may correspond to the same
> +                * symbol, we do not care about the processes in annotate,
> +                * set sort order to avoid repeated output.
> +                */
> +               sort_order = "dso,symbol";
>                 if (setup_sorting(NULL) < 0)
>                         usage_with_options(annotate_usage, options);
>         }
> --
> 2.30.GIT
>