linux-kernel - Re: [PATCH 03/19] perf ftrace: select function/function

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Date:   Sat, 6 Jun 2020 22:28:33 +0800
From:   Changbin Du <changbin.du@...il.com>
To:     Namhyung Kim <namhyung@...nel.org>
Cc:     Changbin Du <changbin.du@...il.com>, Jiri Olsa <jolsa@...hat.com>,
        Arnaldo Carvalho de Melo <acme@...nel.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Ingo Molnar <mingo@...hat.com>,
        Steven Rostedt <rostedt@...dmis.org>,
        linux-kernel <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 03/19] perf ftrace: select function/function_graph tracer
 automatically

On Sun, May 31, 2020 at 02:52:23PM +0900, Namhyung Kim wrote:
> Hello,
> 
> On Mon, May 11, 2020 at 12:07 AM Changbin Du <changbin.du@...il.com> wrote:
> >
> > The '-g/-G' options have already implied function_graph tracer should be
> > used instead of function tracer. So the extra option '--tracer' can be
> > killed.
> >
> > This patch changes the behavior as below:
> >   - By default, function tracer is used.
> 
> Why?  You also removed -t/--tracer option.
>
To save typing. By this way, we do not need the -t/--tracer option which is redundant.
When -G is given, it means graph tracer should be used. If not, function tracer.

> >   - If '-g' or '-G' option is on, then function_graph tracer is used.
> 
> I'm ok with this.
> 
> >   - The perf configuration item 'ftrace.tracer' is removed.
> 
> Why?
> 
As explained above, we don't need this option any longer.

> >   - The default filter for -G is to trace all functions.
> 
> There's no reason to use -G option then.  Also It might be confusing
> if it sees an argument - whether it's a function or a workload.
> 
> I just don't know why you want to change this as we have a way to
> change the default tracer already.
> 
> Thanks
> 
> Namhyung

-- 
Cheers,
Changbin Du