linux-kernel - Re: [PATCH v3 6/9] perf c2c: Support AUX trace

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Message-ID: <20201102100823.GB6633@leoy-ThinkPad-X240s>
Date:   Mon, 2 Nov 2020 18:08:23 +0800
From:   Leo Yan <leo.yan@...aro.org>
To:     Jiri Olsa <jolsa@...hat.com>
Cc:     Arnaldo Carvalho de Melo <acme@...nel.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Ingo Molnar <mingo@...hat.com>,
        Mark Rutland <mark.rutland@....com>,
        Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
        Namhyung Kim <namhyung@...nel.org>,
        John Garry <john.garry@...wei.com>,
        Will Deacon <will@...nel.org>,
        Mathieu Poirier <mathieu.poirier@...aro.org>,
        Kemeng Shi <shikemeng@...wei.com>,
        "Naveen N. Rao" <naveen.n.rao@...ux.vnet.ibm.com>,
        Ian Rogers <irogers@...gle.com>, Al Grant <Al.Grant@....com>,
        James Clark <james.clark@....com>,
        Wei Li <liwei391@...wei.com>,
        André Przywara <andre.przywara@....com>,
        linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH v3 6/9] perf c2c: Support AUX trace

Hi Jiri,

On Sat, Oct 31, 2020 at 09:21:03PM +0100, Jiri Olsa wrote:
> On Wed, Oct 28, 2020 at 02:38:10PM +0800, Leo Yan wrote:
> > This patches adds the AUX callbacks in session structure, so support
> > AUX trace for "perf c2c" tool.
> > 
> > Signed-off-by: Leo Yan <leo.yan@...aro.org>
> > ---
> >  tools/perf/builtin-c2c.c | 4 ++++
> >  1 file changed, 4 insertions(+)
> > 
> > diff --git a/tools/perf/builtin-c2c.c b/tools/perf/builtin-c2c.c
> > index 4d1a08e38233..24f4af997aab 100644
> > --- a/tools/perf/builtin-c2c.c
> > +++ b/tools/perf/builtin-c2c.c
> > @@ -369,6 +369,10 @@ static struct perf_c2c c2c = {
> >  		.exit		= perf_event__process_exit,
> >  		.fork		= perf_event__process_fork,
> >  		.lost		= perf_event__process_lost,
> > +		.attr		= perf_event__process_attr,
> > +		.auxtrace_info  = perf_event__process_auxtrace_info,
> > +		.auxtrace       = perf_event__process_auxtrace,
> > +		.auxtrace_error = perf_event__process_auxtrace_error,
> 
> so this will process aux data, but don't you have to
> say which events you want to synthesize?
> 
> like in script/report via --itrace option?

Indeed, we need to assign "session->itrace_synth_opts", otherwise, the
tool cannot output synthesized samples.

I tried to keep this patch set as small as possible, for easier
reviewing.

Comparing to the previous patch set, I moved out the patch "perf
auxtrace: Add option '-M' for memory events" [1] from this patch set,
at the end my purpose is to introduce the itrace option '-M' to
synthesize memory event; and "perf c2c" tool can use memory event
for output result.  Thus "perf c2c" needs to add itrace_synth_opts:

  struct itrace_synth_opts itrace_synth_opts = {
          .set = true,
          .mem = true,            /* Memory samples */
          .default_no_sample = true,
  };

> aybe arm differs from x86 in this, and it's happening
> in the background.. I have no idea ;-)

There should have no any difference between archs for 'itrace'
behaviour.

Since I moved the patch "perf auxtrace: Add option '-M' for memory
events" out from this patch set, thus I also left out the code for
adding itrace_synth_opts.  This introduced confusion for reviewing the
change (sorry!), I will add back the patch "perf auxtrace: Add option
'-M' for memory events" and add itrace_synth_opts for perf mem/c2c in
next patch set.

Thanks,
Leo

[1] https://lore.kernel.org/patchwork/patch/1298072/