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

[Namhyung Kim]

On Fri, 1 Nov 2013 08:55:02 +0100, Ingo Molnar wrote:
> * Namhyung Kim <namhyung@xxxxxxxxxx> wrote:
>
>> > A couple of details:
>> >
>> > 1)
>> >
>> > This is pretty close to SysProf output, right? So why not use the 
>> > well-known SysProf naming and call the first column 'self' and the 
>> > second column 'total'? I think those names are pretty intuitive and 
>> > it would help people who come from SysProf over to perf.
>> 
>> Okay, I can do it. (Although sysprof seems to call it 'cumulative'
>> rather than 'total' - but I think the 'total' is better since it's
>> simpler and shorter.)
>
> So sysprof-1.2 has the following two windows:
>
>  'functions',   with 'self' and 'total' fields
>  'descendants', with 'self' and 'cumulative' fields
>
> 'descendants' appears to be similar to the perf 'dso' concept.

Arh, okay.  Thanks for the info.

>
>> > 2)
>> >
>> > Is it possible to configure the default 'report -g' style, so that 
>> > people who'd like to use it all the time don't have to type '-g 
>> > cumulative' all the time?
>> 
>> Hmm.. maybe I can add support for the 'report.call-graph' config option.
>
> If we display your new 'total' field by default then it's not as 
> pressing to me :)

Do you mean -g cumulative without 'self' column?

>
>> > 3)
>> >
>> > I'd even argue that we enable this reporting feature by default, if 
>> > a data file includes call-chain data: the first column will still 
>> > show the well-known percentage that perf report produces today, the 
>> > second column will be a new feature in essence.
>> >
>> > The only open question would be, by which column should we sort: 
>> > 'sysprof style' sorts by 'total', 'perf style' sorts by 'self'. 
>> > Agreed?
>> 
>> Right, I defaulted to go by 'total'.  But we can add an option for 
>> it.
>
> The purpose would be to allow people to do old-style 'sort by 
> function overhead' output, while still seeing the 'total' field as 
> well.

Right.

>
> Btw., if anyone is interested in improving the GTK front-end, it 
> would be _really_ nice if it had a 'start profiling' button like 
> sysprof has today, with a 'samples' field showing the current number 
> of samples. (We could even improve upon sysprof by adding 'stop' 
> functionality as well ;-)

Wow, I'm impressed that the sysprof doesn't have one. :)

>
> A bit like perf top, except the reporting session is hidden until 
> the user actively requests the profile.
>
> Maybe it could even be called a gtk version of 'perf top', with a 
> button to start/stop collection, with another button to 
> activate/deactivate reporting output, and yet another button to 
> reset the profiling buffer.
>
> With that feature set perf would be a ready sysprof workflow 
> replacement I think. (I've Cc:-ed Pekka, just in case! :-)

Sounds nice.  I'm not sure I can have to a time to do it anytime soon.

>
>> > 4)
>> >
>> > This is not directly related to the new feature you added: 
>> > call-graph profiling still takes quite a bit of time. It might 
>> > make sense to save the ordered histogram to a perf.data.ordered 
>> > file, so that repeat invocations of 'perf report' don't have to 
>> > recalculate everything again and again?
>> >
>> > This file would be maintained transparently and would only be 
>> > re-created when the perf.data file changes, or something like 
>> > that.
>> 
>> Hmm.. good idea.  We may discuss it along with Jiri's multiple 
>> file storage patches.  I haven't had a time to review - maybe next 
>> week.
>
> So Arnaldo tells me that with your and Frederic's latest 
> callgraph-speedup patches the parsing of perf.data got _really_ 
> fast, so maybe my performance complaint is moot and we should delay 
> complicating the primary perf.data file model with a 'cache' until 
> your patches are in and we see the full impact.

Okay, let's see what happens. :)

Thanks,
Namhyung
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