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

Namhyung Kim
2013-11-01T09:22:33Z

On Fri, 1 Nov 2013 08:55:02 +0100, Ingo Molnar wrote:
> * Namhyung Kim <namhyung@kernel.org> 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