linux-kernel - Re: [PATCH v2 1/5] perf diff: don't compute Delta if he->dummy

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Date:	Wed, 27 Nov 2013 15:23:41 +0530
From:	Ramkumar Ramachandra <artagnon@...il.com>
To:	Jiri Olsa <jolsa@...hat.com>
Cc:	LKML <linux-kernel@...r.kernel.org>,
	Arnaldo Carvalho de Melo <acme@...hat.com>
Subject: Re: [PATCH v2 1/5] perf diff: don't compute Delta if he->dummy

Jiri Olsa wrote:
>> diff --git a/tools/perf/builtin-diff.c b/tools/perf/builtin-diff.c
>> index 3b67ea2..79e0448 100644
>> --- a/tools/perf/builtin-diff.c
>> +++ b/tools/perf/builtin-diff.c
>> @@ -792,6 +792,9 @@ hpp__entry_pair(struct hist_entry *he, struct hist_entry *pair,
>>
>>       switch (idx) {
>>       case PERF_HPP_DIFF__DELTA:
>> +             if (he->dummy)
>> +                     break;
>> +
>
> the reason I disabled the computation for dummy pairs was
> that the number (ratio and weighted diff) would not make much
> sense (to me) without the real pair
>
> but within the dummy delta column we actually see the compared
> file % overheader which is helpfull, even if there's no real pair
> in the baseline

Wait a minute. Doesn't your comment on [3/5] apply here too?
__hpp__entry_global() computes and checks `pair' before calling
hpp__entry_pair(). If he->dummy is set, it means that `he' doesn't
have any pairs: which means that hpp_entry_pair() wouldn't have been
called by __hpp_entry_global() in the first place. So aren't the
he->dummy checks in the RATIO and WEIGHTED_DIFF case redundant?
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