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

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Date:   Mon, 15 Mar 2021 16:47:11 +0800
From:   Yang Jihong <yangjihong1@...wei.com>
To:     Namhyung Kim <namhyung@...nel.org>,
        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

Hi,

On 2021/3/13 11:06, Namhyung Kim wrote:
> 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
> 
Is it changed to the following?
--- 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";
         if ((use_browser == 1 || annotate.use_stdio2) && 
annotate.has_br_stack) {
                 sort__mode = SORT_MODE__BRANCH;
                 if (setup_sorting(annotate.session->evlist) < 0)

I think branch stack mode also don't care about the processes.

>> ---
>>   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
>>
> .
>