linux-kernel - Re: [PATCH v6] perf annotate: Fix sample events lost in stdio mode

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Date:   Thu, 18 Mar 2021 15:13:37 +0900
From:   Namhyung Kim <namhyung@...nel.org>
To:     Yang Jihong <yangjihong1@...wei.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>,
        Yao Jin <yao.jin@...ux.intel.com>, gustavoars@...nel.org,
        mliska@...e.cz, linux-kernel <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v6] perf annotate: Fix sample events lost in stdio mode

Hello,

On Wed, Mar 17, 2021 at 6:44 PM 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.
>
> Signed-off-by: Yang Jihong <yangjihong1@...wei.com>
> ---
>
> Changes since v5:
>   - Add Signed-off-by tag.
>
> Changes since v4:
>   - Use the same sort key "dso,symbol" in branch stack mode.
>
> Changes since v3:
>   - Modify the first line of comments.
>
> Changes since v2:
>   - Remove zfree in hists__find_annotations.
>   - Change sort order to avoid duplicate output.
>
> Changes since v1:
>   - Change processed flag variable from u8 to bool.
>
>  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..92c55f292c11 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);
>                 }
>         }
>  }
> @@ -619,6 +612,12 @@ int cmd_annotate(int argc, const char **argv)
>
>         setup_browser(true);
>
> +       /*
> +        * 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";

At this point, I think there's not much value having separate
setup_sorting() for branch mode.

Thanks,
Namhyung


>         if ((use_browser == 1 || annotate.use_stdio2) && annotate.has_br_stack) {
>                 sort__mode = SORT_MODE__BRANCH;
>                 if (setup_sorting(annotate.session->evlist) < 0)
> --
> 2.30.GIT
>