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

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Date:   Tue, 28 Aug 2018 19:41:31 -0700
From:   Stephane Eranian <eranian@...gle.com>
To:     LKML <linux-kernel@...r.kernel.org>
Cc:     Jiri Olsa <jolsa@...nel.org>,
        Arnaldo Carvalho de Melo <acme@...nel.org>,
        Namhyung Kim <namhyung@...nel.org>,
        Peter Zijlstra <peterz@...radead.org>
Subject: [RFC] perf script: callchain handling is not useful

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.

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.