linux-kernel - Re: [PATCH v3 3/9] perf annotate: Fix wrong --show-total-period option showing number of samples

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Date:   Sun, 23 Jul 2017 07:46:05 +0900
From:   Namhyung Kim <namhyung@...nel.org>
To:     Arnaldo Carvalho de Melo <acme@...nel.org>
Cc:     Taeung Song <treeze.taeung@...il.com>,
        linux-kernel@...r.kernel.org, Milian Wolff <milian.wolff@...b.com>,
        Jiri Olsa <jolsa@...hat.com>, kernel-team@....com,
        Andi Kleen <andi@...stfloor.org>
Subject: Re: [PATCH v3 3/9] perf annotate: Fix wrong --show-total-period
 option showing number of samples

Hi Arnaldo and Taeung,

(+ Andi)

On Fri, Jul 21, 2017 at 11:47:48AM -0300, Arnaldo Carvalho de Melo wrote:
> Em Thu, Jul 20, 2017 at 06:36:55AM +0900, Taeung Song escreveu:
> > +++ b/tools/perf/builtin-annotate.c
> > @@ -177,14 +177,12 @@ static int perf_evsel__add_sample(struct perf_evsel *evsel,
> >  	 */
> >  	process_branch_stack(sample->branch_stack, al, sample);
> >  
> > -	sample->period = 1;
> >  	sample->weight = 1;
> > -
> >  	he = hists__add_entry(hists, al, NULL, NULL, NULL, sample, true);
> >  	if (he == NULL)
> >  		return -ENOMEM;
> 
> I split the hunk above into a separate patch, as a fix, Namhyung, can
> you take a look at why need to unconditionally overwrite what is in
> sample->weight as well?
> 
> Looks fishy as it may come with a value from the kernel, parsed in
> perf_evsel__parse_sample(), when PERF_SAMPLE_WEIGHT is in
> perf_event_attr->sample_type.
> 
> Is it that the hists code needs a sane value when PERF_SAMPLE_WEIGHT
> isn't requested in sample_type?

It was Andi added that code originally (05484298cbfe).  IIUC the
weight is only meaningful for some CPUs with Intel TSX and he used a
dummy value.

AFAIK the hists code doesn't care of it unless weight sort key is used
(for report).  As it's not used by annotate code, I think it'd be
better leaving it as is (like period).

Thanks,
Namhyung


> 
> The resulting cset is below.
> 
> - Arnaldo
> 
> commit a935e8cd8d5d4b7936c4b4cf27c2d0e87d1a6a66
> Author: Taeung Song <treeze.taeung@...il.com>
> Date:   Fri Jul 21 11:38:48 2017 -0300
> 
>     perf annotate: Do not overwrite sample->period
>     
>     In fixing the --show-total-period option it was noticed that the value
>     of sample->period was being overwritten, fix it.
>     
>     Cc: Jiri Olsa <jolsa@...hat.com>
>     Cc: Milian Wolff <milian.wolff@...b.com>
>     Cc: Namhyung Kim <namhyung@...nel.org>
>     Fixes: fd36f3dd7933 ("perf hist: Pass struct sample to __hists__add_entry()")
>     [ split from a larger patch, added the Fixes tag ]
>     Signed-off-by: Arnaldo Carvalho de Melo <acme@...hat.com>
> 
> diff --git a/tools/perf/builtin-annotate.c b/tools/perf/builtin-annotate.c
> index 96fe1a88c1e5..7e33278eff67 100644
> --- a/tools/perf/builtin-annotate.c
> +++ b/tools/perf/builtin-annotate.c
> @@ -177,7 +177,6 @@ static int perf_evsel__add_sample(struct perf_evsel *evsel,
>  	 */
>  	process_branch_stack(sample->branch_stack, al, sample);
>  
> -	sample->period = 1;
>  	sample->weight = 1;
>  
>  	he = hists__add_entry(hists, al, NULL, NULL, NULL, sample, true);