linux-kernel - Re: [PATCH] perf report: Fix hierarchy mode on pipe input

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Date:   Tue, 24 Oct 2023 20:42:45 -0700
From:   Ian Rogers <irogers@...gle.com>
To:     Namhyung Kim <namhyung@...nel.org>
Cc:     Arnaldo Carvalho de Melo <acme@...nel.org>,
        Jiri Olsa <jolsa@...nel.org>,
        Adrian Hunter <adrian.hunter@...el.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Ingo Molnar <mingo@...nel.org>,
        LKML <linux-kernel@...r.kernel.org>,
        linux-perf-users@...r.kernel.org
Subject: Re: [PATCH] perf report: Fix hierarchy mode on pipe input

On Tue, Oct 24, 2023 at 5:31 PM Namhyung Kim <namhyung@...nel.org> wrote:
>
> The hierarchy mode needs to setup output formats for each evsel.
> Normally setup_sorting() handles this at the beginning, but it cannot
> do that if data comes from a pipe since there's no evsel info before
> reading the data.  And then perf report cannot process the samples
> in hierarchy mode and think as if there's no sample.
>
> Let's check the condition and setup the output formats after reading
> data so that it can find evsels.
>
> Before:
>
>   $ ./perf record -o- true | ./perf report -i- --hierarchy -q
>   [ perf record: Woken up 1 times to write data ]
>   [ perf record: Captured and wrote 0.000 MB - ]
>   Error:
>   The - data has no samples!
>
> After:
>
>   $ ./perf record -o- true | ./perf report -i- --hierarchy -q
>   [ perf record: Woken up 1 times to write data ]
>   [ perf record: Captured and wrote 0.000 MB - ]
>       94.76%        true
>          94.76%        [kernel.kallsyms]
>             94.76%        [k] filemap_fault
>        5.24%        perf-ex
>           5.24%        [kernel.kallsyms]
>              5.06%        [k] __memset
>              0.18%        [k] native_write_msr
>
> Signed-off-by: Namhyung Kim <namhyung@...nel.org>

Acked-by: Ian Rogers <irogers@...gle.com>

Thanks,
Ian

> ---
>  tools/perf/builtin-report.c | 15 +++++++++++++++
>  1 file changed, 15 insertions(+)
>
> diff --git a/tools/perf/builtin-report.c b/tools/perf/builtin-report.c
> index dcedfe00f04d..ca8f2331795c 100644
> --- a/tools/perf/builtin-report.c
> +++ b/tools/perf/builtin-report.c
> @@ -691,10 +691,25 @@ static int report__browse_hists(struct report *rep)
>
>  static int report__collapse_hists(struct report *rep)
>  {
> +       struct perf_session *session = rep->session;
> +       struct evlist *evlist = session->evlist;
>         struct ui_progress prog;
>         struct evsel *pos;
>         int ret = 0;
>
> +       /*
> +        * The pipe data needs to setup hierarchy hpp formats now, because it
> +        * cannot know about evsels in the data before reading the data.  The
> +        * normal file data saves the event (attribute) info in the header
> +        * section, but pipe does not have the luxury.
> +        */
> +       if (perf_data__is_pipe(session->data)) {
> +               if (perf_hpp__setup_hists_formats(&perf_hpp_list, evlist) < 0) {
> +                       ui__error("Failed to setup hierachy output formats\n");
> +                       return -1;
> +               }
> +       }
> +
>         ui_progress__init(&prog, rep->nr_entries, "Merging related events...");
>
>         evlist__for_each_entry(rep->session->evlist, pos) {
> --
> 2.42.0.758.gaed0368e0e-goog
>