linux-kernel - Re: [PATCH 1/3] perf hists: Exchange order of comparing items when collapsing hists

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Message-ID: <87fw3lc1ay.fsf@kernel.org>
Date:	Tue, 04 Dec 2012 23:57:41 +0900
From:	Namhyung Kim <namhyung@...nel.org>
To:	Arnaldo Carvalho de Melo <acme@...stprotocols.net>
Cc:	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	Paul Mackerras <paulus@...ba.org>,
	Ingo Molnar <mingo@...nel.org>,
	LKML <linux-kernel@...r.kernel.org>,
	Namhyung Kim <namhyung.kim@....com>,
	Jiri Olsa <jolsa@...hat.com>,
	Stephane Eranian <eranian@...gle.com>
Subject: Re: [PATCH 1/3] perf hists: Exchange order of comparing items when collapsing hists

On Tue, 4 Dec 2012 10:44:05 -0300, Arnaldo Carvalho de Melo wrote:
> Em Tue, Dec 04, 2012 at 01:44:23PM +0900, Namhyung Kim escreveu:
>> From: Namhyung Kim <namhyung.kim@....com>
>> 
>> When comparing entries for collapsing put the given entry first, and
>> then the iterated entry.  This is not the case of hist_entry__cmp()
>> when called if given sort keys don't require collapsing.  So change
>> the order for the sake of consistency.  It will be required for
>> matching and/or linking multiple hist entries.
>> 
>> Cc: Jiri Olsa <jolsa@...hat.com>
>> Cc: Stephane Eranian <eranian@...gle.com>
>> Signed-off-by: Namhyung Kim <namhyung@...nel.org>
>> ---
>>  tools/perf/util/hist.c | 2 +-
>>  1 file changed, 1 insertion(+), 1 deletion(-)
>> 
>> diff --git a/tools/perf/util/hist.c b/tools/perf/util/hist.c
>> index 82df1b26f0d4..161c35e7ed0e 100644
>> --- a/tools/perf/util/hist.c
>> +++ b/tools/perf/util/hist.c
>> @@ -433,7 +433,7 @@ static bool hists__collapse_insert_entry(struct hists *hists __maybe_unused,
>>  		parent = *p;
>>  		iter = rb_entry(parent, struct hist_entry, rb_node_in);
>>  
>> -		cmp = hist_entry__collapse(iter, he);
>> +		cmp = hist_entry__collapse(he, iter);
>>  
>>  		if (!cmp) {
>>  			he_stat__add_stat(&iter->stat, &he->stat);
>
> What about this he_stat__add_stat call? Now the hist_entry__collapse
> receives (he, iter)  while this right next function call receives (iter,
> he).

Hmm.. I thought they're diffent kind of operation.  hist_entry__collapse
is in a process of iteration and he_stat__add_stat is not.  It's just
adding or copying entry's stat, so I thought it's something like memcpy
- hence the order.

If you really concern about ordering between them, maybe I can change
hist_entry__cmp() to receive (iter, he).

Thanks,
Namhyung
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