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

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Message-ID: <CAM9d7cgAxg_=1ZZHh0JPCRJpH1mpfcR50vu8MAGnQP7WThBpqg@mail.gmail.com>
Date:   Sun, 31 May 2020 14:52:23 +0900
From:   Namhyung Kim <namhyung@...nel.org>
To:     Changbin Du <changbin.du@...il.com>
Cc:     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

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.

>   - 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?

>   - 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