linux-kernel - Re: [PATCH v8 05/18] perf ftrace: show trace column header

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Message-ID: <20200814115655.GU13995@kernel.org>
Date:   Fri, 14 Aug 2020 08:56:55 -0300
From:   Arnaldo Carvalho de Melo <acme@...nel.org>
To:     Changbin Du <changbin.du@...il.com>
Cc:     Jiri Olsa <jolsa@...hat.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Ingo Molnar <mingo@...hat.com>,
        Namhyung Kim <namhyung@...nel.org>,
        Steven Rostedt <rostedt@...dmis.org>,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v8 05/18] perf ftrace: show trace column header

Em Sat, Aug 08, 2020 at 10:31:28AM +0800, Changbin Du escreveu:
> This makes perf-ftrace display column header before printing trace.
> 
>   $ sudo perf ftrace
>   # tracer: function
>   #
>   # entries-in-buffer/entries-written: 0/0   #P:8
>   #
>   #            TASK-PID     CPU#   TIMESTAMP  FUNCTION
>   #              | |         |       |         |
>              <...>-9246  [006]  10726.262760: mutex_unlock <-rb_simple_write
>              <...>-9246  [006]  10726.262764: __fsnotify_parent <-vfs_write
>              <...>-9246  [006]  10726.262765: fsnotify <-vfs_write
>              <...>-9246  [006]  10726.262766: __sb_end_write <-vfs_write
>              <...>-9246  [006]  10726.262767: fpregs_assert_state_consistent <-do_syscall_64

We have:

  # perf report -h header
  
   Usage: perf report [<options>]
  
          --header          Show data header.
          --header-only     Show only data header.
  
  #

So perhaps we should have those as well, in the 'ftrace' case one would
perhaps want to use --no-header, for instance, to do some scripting
parsing just the trace lines.

- Arnaldo
 
> Signed-off-by: Changbin Du <changbin.du@...il.com>
> ---
>  tools/perf/builtin-ftrace.c | 3 +++
>  1 file changed, 3 insertions(+)
> 
> diff --git a/tools/perf/builtin-ftrace.c b/tools/perf/builtin-ftrace.c
> index a3a4f4be9dde..39c694be2b71 100644
> --- a/tools/perf/builtin-ftrace.c
> +++ b/tools/perf/builtin-ftrace.c
> @@ -435,6 +435,9 @@ static int __cmd_ftrace(struct perf_ftrace *ftrace, int argc, const char **argv)
>  	fcntl(trace_fd, F_SETFL, O_NONBLOCK);
>  	pollfd.fd = trace_fd;
>  
> +	/* display column headers */
> +	read_tracing_file_to_stdout("trace");
> +
>  	if (write_tracing_file("tracing_on", "1") < 0) {
>  		pr_err("can't enable tracing\n");
>  		goto out_close_fd;
> -- 
> 2.25.1
> 

-- 

- Arnaldo