linux-kernel - Re: [RFC/PATCHSET 00/14] perf report: Add support to accumulate hist periods (v2)

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Date:	Wed, 06 Nov 2013 18:17:45 +0900
From:	Namhyung Kim <namhyung@...nel.org>
To:	Ingo Molnar <mingo@...nel.org>
Cc:	Pekka Enberg <penberg@...nel.org>,
	Arnaldo Carvalho de Melo <acme@...stprotocols.net>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	Paul Mackerras <paulus@...ba.org>,
	Namhyung Kim <namhyung.kim@....com>,
	LKML <linux-kernel@...r.kernel.org>,
	Frederic Weisbecker <fweisbec@...il.com>,
	Stephane Eranian <eranian@...gle.com>,
	Jiri Olsa <jolsa@...hat.com>,
	Rodrigo Campos <rodrigo@...g.com.ar>,
	Arun Sharma <asharma@...com>
Subject: Re: [RFC/PATCHSET 00/14] perf report: Add support to accumulate hist periods (v2)

On Wed, 6 Nov 2013 09:30:46 +0100, Ingo Molnar wrote:
> * Namhyung Kim <namhyung@...nel.org> wrote:
>
>> Hi Ingo,
>> 
>> On Tue, 5 Nov 2013 12:58:02 +0100, Ingo Molnar wrote:
>> > * Namhyung Kim <namhyung@...nel.org> wrote:
>> >> But the 'cumulative' (btw, I feel a bit hard to type this word..) is 
>> >> different in that it *generates* entries didn't get sampled originally. 
>> >> And as it requires callchains, total field will not work if callchains 
>> >> are missing.
>> >
>> > Well, 'total' should disappear if it's not available.
>> 
>> But what if it's the only sort key user gave?
>
> Do you mean something like:
>
>   -F self,name -s total
>
> i.e. if a sort key not displayed?

What I worry is when no -F option was given at all.

>
> I think sort keys should be automatically added to the displayed fields 
> list.

Agreed.

>
> This rule is obviously met with the -F total:2,self:1,name:0 kind of 
> sorting syntax (you can only sort by fields that get displayed) - if mixed 
> with -s then it should be implicit I think.
>
>> >> But for compatibility we need to use 'self' sort key internally iff 
>> >> neither the -F option nor the config option was given by user.  And 
>> >> it might warn (or notice) users to add 'self' column in the sort key 
>> >> for future use.
>> >
>> > Mind explaining what the problem here is? I don't think I get it.
>> 
>> Well, normal users still use it as they used to - like 
>> 'perf report -s comm,dso' without -F option and the config.
>> 
>> In that case, what would the output look like?  According to the above
>> proposal it'd look like below.
>> 
>>   # Command  Shared object
>>   # .......  .............
>>         aaa  aaa
>>         aaa  libc.so
>>         bbb  bbb
>>         bbb  libc.so
>> 
>> 
>> But the user might want see this:
>> 
>>   # Overhead (self)  Command  Shared object
>>   # ...............  .......  .............
>>              30.00%      bbb  bbb
>>              25.00%      aaa  aaa
>>              25.00%      aaa  libc.so
>>              20.00%      bbb  libc.so
>> 
>> 
>> If she really wants to see it sorted by comm and dso, the command line
>> should be 'perf report -F self,comm,dso -s comm,dso'
>> (or just 'perf report -F self -s comm,dso' could do the same).
>> 
>>   # Overhead (self)  Command  Shared object
>>   # ...............  .......  .............
>>              25.00%      aaa  aaa
>>              25.00%      aaa  libc.so
>>              30.00%      bbb  bbb
>>              20.00%      bbb  libc.so
>
> This problem should be solved if all -s fields are displayed - i.e. they 
> are added to the -F list, right?

But old users might not aware of the new -F option, and use -s option
only.  If so, she will get output like the first example, right?

>
> Basically there's just a single concept: the -F list. The -s option simply 
> modifies and extends the -F list but internally perf report would not know 
> anything about '-s', it only knows about fields to display and it would 
> know which of those fields are to be sorted and in what order.
>
> Does that make sense to you? Does it cover everything needed?

I like the concept.  I'm just looking for a way to add it without
upsetting old users. :)

Thanks,
Namhyung
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