linux-kernel - Re: [RFC] perf script: callchain handling is not useful

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Date:   Wed, 29 Aug 2018 08:14:12 -0700
From:   Stephane Eranian <eranian@...gle.com>
To:     Arnaldo Carvalho de Melo <acme@...nel.org>
Cc:     LKML <linux-kernel@...r.kernel.org>, Jiri Olsa <jolsa@...nel.org>,
        Namhyung Kim <namhyung@...nel.org>,
        Peter Zijlstra <peterz@...radead.org>
Subject: Re: [RFC] perf script: callchain handling is not useful

On Wed, Aug 29, 2018 at 6:54 AM Arnaldo Carvalho de Melo
<acme@...nel.org> wrote:
>
> Em Tue, Aug 28, 2018 at 07:41:31PM -0700, Stephane Eranian escreveu:
> > Hi,
> >
> > I am doing the following simple collection with callchain and load profiling:
> >
> > $ perf record -g -d -e cpu/event=0xd0,umask=0x81/pp  my_test_program
> >
> > But when I type:
> > $ perf script -F ip,addr
> > ffff9d4821346878
> >         ffffffff9d58df25
> >         ffffffff9d58e054
> >         ffffffff9d5965bb
> >         ffffffff9d640650
> >         ffffffff9d697d06
> >         ffffffff9d63ec60
> >         ffffffff9d640322
> >         ffffffff9d64070c
> >         ffffffff9d455a60
> >                   7030c7
> >
> > ffff9d4638ba84a0
> >         ffffffff9d5df447
> >         ffffffff9d5eaf4a
> >         ffffffff9d63e165
> >         ffffffff9d63e439
> >         ffffffff9d697d98
> >         ffffffff9d63ec60
> >         ffffffff9d640322
> >         ffffffff9d64070c
> >         ffffffff9d455a60
> >                   7030c7
> > I also see the callchain and it is not clear which is the IP. Further
> > more parsing becomes more difficult because of multiple lines per
> > sample. I understand that multiline is likely because of
> > symbolization. But if I don't want symbolization, it should be
> > possible to print all in one line.
>
> Humm, to have this not break possibly existing scripts, perhaps we can
> have something like:
>
>   $ perf script -F ip,-callchain,addr
>
> ?
>
> And if asked explicitely for the callchain, then it gets added in the
> same line?
>
Yeah, that should do it.
Thanks.

> - Arnaldo
>
>
> > The current output is not very useful. You expect perf script to give
> > you one line per sample and only what you want. Callchain != IP.
> >
> > I think the following should happen:
> >   - do not print callchain when asked for the IP. Create a callchain filter.
> >   - print callchain on the same line, much like what is done for brstack
> >
> > It is not clear to me why callchain and ip were lumped together.
> > Any opinion on my proposal?
> > Thanks.