linux-kernel - Re: [PATCH 4/9] perf stat: Remove transaction

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Date:	Wed, 3 Jun 2015 12:55:43 -0300
From:	Arnaldo Carvalho de Melo <acme@...nel.org>
To:	Jiri Olsa <jolsa@...hat.com>
Cc:	Jiri Olsa <jolsa@...nel.org>, lkml <linux-kernel@...r.kernel.org>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	Paul Mackerras <paulus@...ba.org>,
	David Ahern <dsahern@...il.com>,
	Namhyung Kim <namhyung@...nel.org>,
	Ingo Molnar <mingo@...nel.org>,
	Andi Kleen <ak@...ux.intel.com>,
	Stephane Eranian <eranian@...gle.com>
Subject: Re: [PATCH 4/9] perf stat: Remove transaction_run from shadow
 update/print code

Em Wed, Jun 03, 2015 at 05:14:50PM +0200, Jiri Olsa escreveu:
> On Wed, Jun 03, 2015 at 12:10:38PM -0300, Arnaldo Carvalho de Melo wrote:
> > Em Wed, Jun 03, 2015 at 04:25:54PM +0200, Jiri Olsa escreveu:
> > > It's no longer needed, because we use nameid to recognize
> > > transaction events.
> > > 
> > > Keeping it only in stat code to initialize transaction events.
> > 
> > Lemme see if I understand this correctly, this update_shadow_stats() is
> > called only for transaction runs?
> > 
> > It doesn't seem so, so now we will update those stats all the time?
> 
> update_shadow_stats is called on currently read/processed
> counter and based on its 'type' we update various other
> counters - shadow counters - which are the base for things
> like IPC in the stat output


So:

-       else if (transaction_run && perf_stat_evsel__is(counter, CYCLES_IN_TX))
+       else if (perf_stat_evsel__is(counter, CYCLES_IN_TX))
                update_stats(&runtime_transaction_stats[ctx][cpu], count[0]);


Before we were going to check this _only_ when transaction_run was set,
now we are doing it always, or are you saying that
perf_stat_evsel__is(counter, CYCLES_IN_TX) will only return true for
transaction 'perf stat' usage?

Let me take a look:

Yes, in all cases we, start doing:

   perf_evlist__alloc_stats()
     perf_evsel__alloc_stat_priv()
       perf_evsel__reset_stat_priv()
         perf_stat_evsel_id_init();
           struct perf_stat *ps = evsel->priv;
           ps->id = one of the entries below:

static const char *id_str[PERF_STAT_EVSEL_ID__MAX] = {
        ID(NONE,                x),
        ID(CYCLES_IN_TX,        cpu/cycles-t/),
        ID(TRANSACTION_START,   cpu/tx-start/),
        ID(ELISION_START,       cpu/el-start/),
        ID(CYCLES_IN_TX_CP,     cpu/cycles-ct/),
};


Ok, guess I understood now, all the events above are transaction events,
so if one of them is present, then, yes, this is a transaction run, and
we don't need to look at the 'transaction_run' variable to update the
shadow stats, got it right?

I.e. we _never_ needed to look at 'transaction_id', just noticing that
ps->id is not zero, ok.

- Arnaldo
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