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Date:   Sat, 6 Jun 2020 22:37:17 +0800
From:   Changbin Du <changbin.du@gmail.com>
To:     Arnaldo Carvalho de Melo <arnaldo.melo@gmail.com>
Cc:     Changbin Du <changbin.du@gmail.com>, Jiri Olsa <jolsa@redhat.com>,
        Peter Zijlstra <peterz@infradead.org>,
        Ingo Molnar <mingo@redhat.com>,
        Namhyung Kim <namhyung@kernel.org>,
        Steven Rostedt <rostedt@goodmis.org>,
        linux-kernel@vger.kernel.org
Subject: Re: [PATCH 15/19] perf ftrace: show trace column header
Message-ID: <20200606143717.pxtjbx5hrpuwp4hs@mail.google.com>
References: <20200510150628.16610-1-changbin.du@gmail.com>
 <20200510150628.16610-16-changbin.du@gmail.com>
 <20200520211101.GD32678@kernel.org>
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On Wed, May 20, 2020 at 06:11:01PM -0300, Arnaldo Carvalho de Melo wrote:
> Em Sun, May 10, 2020 at 11:06:24PM +0800, Changbin Du escreveu:
> > This makes perf-ftrace display column header before printing trace.
> 
> [acme@five perf]$ perf report -h header
> 
>  Usage: perf report [<options>]
> 
>         --header          Show data header.
>         --header-only     Show only data header.
> 
> [acme@five perf]$
> 
> Perhaps there is value in --header-only to show the default that will be
> setup when using some set of options.
> 
Arnaldo, what is the '--header-only' option used for? As for ftrace, the header
format is different for different trace 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@gmail.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

-- 
Cheers,
Changbin Du