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Subject: Re: [PATCH v7 01/18] perf ftrace: select function/function_graph tracer automatically
To:     Changbin Du <changbin.du@gmail.com>
CC:     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
From:   Arnaldo Carvalho de Melo <arnaldo.melo@gmail.com>
Message-ID: <E69D6A9B-D2F7-43EA-AD6F-3164F199A6E4@gmail.com>
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On August 5, 2020 9:14:48 PM GMT-03:00, Changbin Du <changbin=2Edu@gmail=
=2Ecom> wrote:
>On Tue, Aug 04, 2020 at 09:51:15AM -0300, Arnaldo Carvalho de Melo
>wrote:
>> Em Sat, Jul 18, 2020 at 02:48:09PM +0800, Changbin Du escreveu:
>> > The '-g/-G' options have already implied function_graph tracer
>should be
>> > used instead of function tracer=2E So the extra option '--tracer' can
>be
>> > killed=2E
>> >=20
>> > This patch changes the behavior as below:
>> >   - By default, function tracer is used=2E
>> >   - If '-g' or '-G' option is on, then function_graph tracer is
>used=2E
>> >   - The perf configuration item 'ftrace=2Etracer' is marked as
>deprecated=2E
>> >   - The option '--tracer' is marked as deprecated=2E
>>=20
>> You should try to be more granular, for instance, I think the
>decision
>> to change the default is questionable, but could be acceptable=2E
>>=20
>> But why deprecate the perf configuration for the default tracer?
>>=20
>> Say people who already use 'perf ftrace ls' go and use with this
>patch
>> and see that it changed the default from the function_graph tracer to
>> the function tracer and disagree with you, they want the default to
>be
>> the function graph tracer, know that there is (or there was) a
>> ftrace=2Etracer in ~/=2Eprefconfig, and then try that, only to find out
>that
>> it is not possible, frustrating :-\
>>=20
>> So can we please remove this deprecation of ftrace=2Etracer so that
>people
>> used to how it was can get that behaviour back?
>>=20
>Agreed=2E If no -F or -G is given, we can use the ftrace=2Etracer as
>default tracer=2E
>Let me update it=2E Thanks=2E

Thanks, I'm general try to be as granular as possible, doing one thing per=
 patch, this way the reviewer can do some preliminary cherry picking and we=
 also improve git bisectability=2E

- Arnaldo

--=20
Sent from my Android device with K-9 Mail=2E Please excuse my brevity=2E