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

    * 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.

    > > 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 :)

    > > 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.

    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 ;-)

    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! :-)

    > > 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.

    Thanks,

    Ingo


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