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Date: Mon, 2 Dec 2013 15:49:05 -0300
From: Arnaldo Carvalho de Melo <acme@ghostprotocols.net>
To: Namhyung Kim <namhyung@kernel.org>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>, Paul Mackerras <paulus@samba.org>,
        Ingo Molnar <mingo@kernel.org>, Namhyung Kim <namhyung.kim@lge.com>,
        LKML <linux-kernel@vger.kernel.org>, Jiri Olsa <jolsa@redhat.com>,
        David Ahern <dsahern@gmail.com>, Stephane Eranian <eranian@google.com>,
        Andi Kleen <andi@firstfloor.org>, Pekka Enberg <penberg@kernel.org>,
        Frederic Weisbecker <fweisbec@gmail.com>
Subject: Re: [PATCH 2/3] perf tools: Record sampling time for each entry
Message-ID: <20131202184905.GA14254@ghostprotocols.net>
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Em Mon, Dec 02, 2013 at 11:57:44PM +0900, Namhyung Kim escreveu:
> 2013-12-02 (월), 09:39 -0300, Arnaldo Carvalho de Melo:
> > Em Mon, Dec 02, 2013 at 03:53:18PM +0900, Namhyung Kim escreveu:
> > > From: Namhyung Kim <namhyung.kim@lge.com>
> > > 
> > > Calculate elapsed time for each sample and record it.  The elapsed
> > > time is a diff between current sample->time and previous sample->time
> > > which was saved for each evsel and cpu.
> > 
> > Can you elaborate on why this is interesting to have? What meaning can
> > one get from the sample->time - prev_sample->time?
> > 
> > We need clearer changelogs...
> 
> Sorry about that.. how about this?
> 
> Sometimes users might want see a relation between value and time of a
> sample.  And the time itself is a very important information to have.
> As the sample->period value is a diff of counter values between samples
> it might make sense to add time-diff between samples into a hist entry.
> 
> To do that, calculate elapsed time for each sample and record it.  The
> elapsed time is the diff between current sample->time and previous
> sample->time which was saved for each evsel.

Much better! Thanks, and please consider adding this to the man page as
well, in a followup patch.

I'll add the above explanation to the patch, that, as I could read seems
to not have had any nak, right?

- Arnaldo