Re: [RFC/PATCHSET 0/5] perf ftrace: Implement function latency histogram (v1)

From: Namhyung Kim <namhyung@kernel.org>
To: Arnaldo Carvalho de Melo <acme@kernel.org>
Cc: Jiri Olsa <jolsa@redhat.com>, Ingo Molnar <mingo@kernel.org>,
	Peter Zijlstra <peterz@infradead.org>,
	LKML <linux-kernel@vger.kernel.org>,
	Andi Kleen <ak@linux.intel.com>, Ian Rogers <irogers@google.com>,
	Stephane Eranian <eranian@google.com>,
	Song Liu <songliubraving@fb.com>,
	Changbin Du <changbin.du@gmail.com>
Subject: Re: [RFC/PATCHSET 0/5] perf ftrace: Implement function latency histogram (v1)
Date: Tue, 30 Nov 2021 14:58:08 -0800	[thread overview]
Message-ID: <CAM9d7cjXncRRsH1Zf_yVrLeaYiHXLFM29sx0MYPAZ8HAsZaggw@mail.gmail.com> (raw)
In-Reply-To: <YaY3JqOQ2XE22VId@kernel.org>

Hi Arnaldo,

On Tue, Nov 30, 2021 at 6:37 AM Arnaldo Carvalho de Melo
<acme@kernel.org> wrote:
>
> Em Mon, Nov 29, 2021 at 03:18:25PM -0800, Namhyung Kim escreveu:
> > Hello,
> >
> > I've implemented 'latency' subcommand in the perf ftrace command to
> > show a histogram of function latency.
> >
> > To handle new subcommands, the existing functionality is moved to
> > 'trace' subcommand while preserving backward compatibility of not
> > having a subcommand at all (defaults to 'trace').
> >
> > The latency subcommand accepts a target (kernel, for now) function
> > with -T option and shows a histogram like below:
>
> Humm, wouldn't be interesting to shorten this by having a new 'perf
> flat' (function latency) tool, on the same level as 'perf ftrace' and
> leave 'perf ftrace' to just being a convenient perf interface to what
> ftrace provides?

That would be fine.  I also think 'perf ftrace latency' is
bit too long.  But if we would add a new feature
like argdist (in BCC) later, I thought it'd be nice being
a subcommand in the perf ftrace together.

But it's up to you.  I'll make a change if you prefer
'flat' (or how about 'fnlat' instead?).

>
> But all around, nice work, cool new toyz! :-)

Thanks!
Namhyung