linux-kernel - Re: RFC: callchain showing same entry as hist

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Date:	Wed, 17 Aug 2016 00:23:55 +0900
From:	Namhyung Kim <namhyung@...nel.org>
To:	Arnaldo Carvalho de Melo <acme@...nel.org>
Cc:	Jiri Olsa <jolsa@...nel.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: RFC: callchain showing same entry as hist_entry

On Tue, Aug 16, 2016 at 12:08:03PM -0300, Arnaldo Carvalho de Melo wrote:
> Em Tue, Aug 16, 2016 at 11:55:11PM +0900, Namhyung Kim escreveu:
> > Hi Arnaldo,
> > 
> > On Tue, Aug 16, 2016 at 11:36:28AM -0300, Arnaldo Carvalho de Melo wrote:
> > > Hi Namhyung, Jiri,
> > > 
> > > 	please take a look at the patch below, and Ack if possible, it
> > > is a problem introduced in:
> > > 
> > >   cfaa154b2335 ("perf tools: Get rid of obsolete hist_entry__sort_list")
> > > 
> > > That is not equivalent to the code that was there and results in having
> > > the same entry as the first entry for the callchain as in the
> > > hist_entry, which is annoying and doesn't match the original intent of
> > > that 'continue' branch, as described in the comment right above it.
> > 
> > AFAIK the intent was to skip first callchain entry iff the first sort
> > key is 'symbol'.  The sort_order being NULL means it'd use the default
> > sort key which is 'comm,dso,sym' so it should not skip the first
> > callchain entry.
> > 
> > The original code (before cfaa154b2335) was like below:
> > 
> > -                       if (!i++ && sort__first_dimension == SORT_SYM)
> > +                       if (!i++ && field_order == NULL &&
> > +                           sort_order && !prefixcmp(sort_order, "sym"))
> > 
> > I think the current code works as intended, no?
> 
> Well, see below the cset comment (local one, will change as we discuss),
> may clarify further, but yeah, we can't take for granted that the
> default sort order has "sym" in it :-\
> 
> So the original intent description was ambiguous, what we want to avoid
> is what is in the cset comment below, so the logic for that should be a
> bit different, tho.
> 
> For starters we need to have a callchain_something__first() that will
> skip the first one using this logic and then use it in all places in
> --stdio, --tui, --gtk where we need this.
> 
> commit c066eaa8d06b87c77b82d55bbc59be308aca4684
> Author: Arnaldo Carvalho de Melo <acme@...hat.com>
> Date:   Tue Aug 16 11:36:50 2016 -0300
> 
>     perf callchain: Do not repeat the hist_entry symbol as the 1st callchain entry
>     
>     We were getting:
>     
>          2.62%  [k] __d_lookup_rcu
>                 |
>                 ---__d_lookup_rcu
>                    |
>                     --2.52%--lookup_fast
>                               |
>                                --2.50%--walk_component
>     
>     Noticed the __d_lookup_rcu dup, when the original coder intent, and the saner
>     output is:
>     
>          2.62%  [k] __d_lookup_rcu
>                 |
>                  --2.52%--lookup_fast
>                            |
>                             --2.50%--walk_component
>     
>     This is for --stdio, TUI being investigated.

Did you run 'perf report -s sym --stdio'?  It seems that current code
already works as sane..  Do you want to make it work for the default sort
key too?

Thanks,
Namhyung


>     
>     Cc: Adrian Hunter <adrian.hunter@...el.com>
>     Cc: David Ahern <dsahern@...il.com>
>     Cc: Jiri Olsa <jolsa@...nel.org>
>     Cc: Linus Torvalds <torvalds@...ux-foundation.org>
>     Cc: Namhyung Kim <namhyung@...nel.org>
>     Cc: Wang Nan <wangnan0@...wei.com>
>     Fixes: cfaa154b2335 ("perf tools: Get rid of obsolete hist_entry__sort_list")
>     Link: http://lkml.kernel.org/r/20160816143628.GG20972@kernel.org
>     Signed-off-by: Arnaldo Carvalho de Melo <acme@...hat.com>
> 
> diff --git a/tools/perf/ui/stdio/hist.c b/tools/perf/ui/stdio/hist.c
> index 9b65f4a6b35a..46a083e59ce9 100644
> --- a/tools/perf/ui/stdio/hist.c
> +++ b/tools/perf/ui/stdio/hist.c
> @@ -207,7 +207,7 @@ static size_t callchain__fprintf_graph(FILE *fp, struct rb_root *root,
>  			 * displayed twice.
>  			 */
>  			if (!i++ && field_order == NULL &&
> -			    sort_order && !prefixcmp(sort_order, "sym"))
> +			    (sort_order == NULL || !prefixcmp(sort_order, "sym")))
>  				continue;
>  			if (!printed) {
>  				ret += callchain__fprintf_left_margin(fp, left_margin);