linux-kernel - Re: [PATCH 05/13] perf hists: Resort hist entries using group members for output

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Message-ID: <87mww9mqlt.fsf@sejong.aot.lge.com>
Date:	Wed, 16 Jan 2013 18:20:14 +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>,
	Jiri Olsa <jolsa@...hat.com>,
	Stephane Eranian <eranian@...gle.com>,
	Namhyung Kim <namhyung.kim@....com>
Subject: Re: [PATCH 05/13] perf hists: Resort hist entries using group members for output

Hi Arnaldo,

On Tue, 15 Jan 2013 15:29:15 -0300, Arnaldo Carvalho de Melo wrote:
> Em Tue, Jan 15, 2013 at 04:31:49PM +0900, Namhyung Kim escreveu:
>> From: Namhyung Kim <namhyung.kim@....com>
>> 
>> When event group is enabled, sorting hist entries on periods for output
>> should consider groups members' period also.  To do that, build period
>> table using link/pair information and compare the table.
[snip]
>> +static int hist_entry__sort_on_period(struct hist_entry *a,
>> +				      struct hist_entry *b)
>> +{
>> +	int ret;
>> +	int i, nr_members;
>> +	struct perf_evsel *evsel;
>> +	struct hist_entry *pair;
>> +	u64 *periods_a, *periods_b;
>> +
>> +	ret = period_cmp(a->stat.period, b->stat.period);
>> +	if (ret || !symbol_conf.event_group)
>
> Why do we need to call period_cmp() when symbol_conf.event_group is
> false?
>
> I see, confusing neverthless :-\

In this function @a and @b are entries of group leaders and should be
compared first - other group members are compared only if periods of
leader entries are same.

For non-group events or when event group view is disabled, this function
will be called for every events as if they're leaders.


>
>> +		return ret;
>
> I would expect two functions, one for sorting on period and another for
> not sorting on period, i.e. don't call a function called
> 'sort_on_period' when _not_ sorting on period.

Sorry, I can't understand.

This 'sort_on_period' function is called during the (final) output
resorting and it's unconditional.  IOW hist entries should be sorted by
their period to be shown accordingly in the output.

Am I missing something?

Thanks,
Namhyung
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