linux-kernel - Re: [PATCH 15/19] perf ftrace: show trace column header

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Date:   Wed, 20 May 2020 18:11:01 -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 15/19] perf ftrace: show trace column header

Em Sun, May 10, 2020 at 11:06:24PM +0800, Changbin Du escreveu:
> This makes perf-ftrace display column header before printing trace.

[acme@...e perf]$ perf report -h header

 Usage: perf report [<options>]

        --header          Show data header.
        --header-only     Show only data header.

[acme@...e perf]$

Perhaps there is value in --header-only to show the default that will be
setup when using some set of options.

- Arnaldo

> $ 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
> 
> 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 64c22f367ba2..0b39b6a88026 100644
> --- a/tools/perf/builtin-ftrace.c
> +++ b/tools/perf/builtin-ftrace.c
> @@ -614,6 +614,9 @@ 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