Re: [GIT PULL 0/8] perf/pt -> Intel PT/BTS

Ingo Molnar
2015-06-30T04:59:12Z

* Arnaldo Carvalho de Melo <acme@kernel.org> wrote:

> Hi Ingo,
>
> Please consider pulling, there are several other patches after this,
> but I think that this may be acceptable to showcase the capabilities already
> present, look at the output of 'perf script' and callchains for userspace
> without using any extra debugging info (no need for DWARF, CFI, nothing),
> really cool capabilities... :-)
>
> Adrian wrote some docs and I tested it both on a Ivy Bridge machine
> where there is only BTS and on a Broadwell machine with the whole shebang,
> adding the output of the commands to the csets, to further showcase what is
> there already.
>
> This is on top of my last perf-core-for-mingo tag.
>
> Up to you, please let us know what you think and we'll continue working
> on having this in an acceptable form for merging,
>
> Regards,
>
> - Arnaldo
>
> P.S. Kudos for Adrian for the patience with this process, way more is needed to
> polish this, but the promise is there, cool stuff indeed! :-)
>
> The following changes since commit 36c8bb56a9f718a9a5f35d1834ca9dcec95deb4a:
>
> perf symbols: Check access permission when reading symbol files (2015-06-26 12:11:53 -0300)
>
> are available in the git repository at:
>
> git://git.kernel.org/pub/scm/linux/kernel/git/acme/linux.git tags/perf-pt-for-mingo
>
> for you to fetch changes up to 04759f172270afb28c8004f5cad62ed55710a499:
>
> perf tools: Add Intel BTS support (2015-06-26 18:36:11 -0300)
>
> ----------------------------------------------------------------
> Put Intel PT and BTS into initial use (Adrian Hunter)
>
> Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
>
> ----------------------------------------------------------------
> Adrian Hunter (8):
> perf auxtrace: Add Intel PT as an AUX area tracing type
> perf tools: Add Intel PT packet decoder
> perf tools: Add Intel PT instruction decoder
> perf tools: Add Intel PT log
> perf tools: Add Intel PT decoder
> perf tools: Add Intel PT support
> perf tools: Take Intel PT into use
> perf tools: Add Intel BTS support
>
> tools/build/Makefile.build | 2 +
> tools/perf/.gitignore | 2 +
> tools/perf/Documentation/intel-bts.txt | 86 +
> tools/perf/Documentation/intel-pt.txt | 588 ++++++
> tools/perf/MANIFEST | 7 +
> tools/perf/Makefile.perf | 12 +-
> tools/perf/arch/x86/util/Build | 5 +
> tools/perf/arch/x86/util/auxtrace.c | 83 +
> tools/perf/arch/x86/util/intel-bts.c | 458 +++++
> tools/perf/arch/x86/util/intel-pt.c | 752 ++++++++
> tools/perf/arch/x86/util/pmu.c | 18 +
> tools/perf/util/Build | 3 +
> tools/perf/util/auxtrace.c | 9 +-
> tools/perf/util/auxtrace.h | 2 +
> tools/perf/util/intel-bts.c | 791 ++++++++
> tools/perf/util/intel-bts.h | 43 +
> tools/perf/util/intel-pt-decoder/Build | 14 +
> .../perf/util/intel-pt-decoder/intel-pt-decoder.c | 1759 ++++++++++++++++++
> .../perf/util/intel-pt-decoder/intel-pt-decoder.h | 102 ++
> .../util/intel-pt-decoder/intel-pt-insn-decoder.c | 246 +++
> .../util/intel-pt-decoder/intel-pt-insn-decoder.h | 65 +
> tools/perf/util/intel-pt-decoder/intel-pt-log.c | 155 ++
> tools/perf/util/intel-pt-decoder/intel-pt-log.h | 52 +
> .../util/intel-pt-decoder/intel-pt-pkt-decoder.c | 400 +++++
> .../util/intel-pt-decoder/intel-pt-pkt-decoder.h | 64 +
> tools/perf/util/intel-pt.c | 1889 ++++++++++++++++++++
> tools/perf/util/intel-pt.h | 51 +
> tools/perf/util/pmu.c | 4 -
> 28 files changed, 7655 insertions(+), 7 deletions(-)
> create mode 100644 tools/perf/Documentation/intel-bts.txt
> create mode 100644 tools/perf/Documentation/intel-pt.txt
> create mode 100644 tools/perf/arch/x86/util/auxtrace.c
> create mode 100644 tools/perf/arch/x86/util/intel-bts.c
> create mode 100644 tools/perf/arch/x86/util/intel-pt.c
> create mode 100644 tools/perf/arch/x86/util/pmu.c
> create mode 100644 tools/perf/util/intel-bts.c
> create mode 100644 tools/perf/util/intel-bts.h
> create mode 100644 tools/perf/util/intel-pt-decoder/Build
> create mode 100644 tools/perf/util/intel-pt-decoder/intel-pt-decoder.c
> create mode 100644 tools/perf/util/intel-pt-decoder/intel-pt-decoder.h
> create mode 100644 tools/perf/util/intel-pt-decoder/intel-pt-insn-decoder.c
> create mode 100644 tools/perf/util/intel-pt-decoder/intel-pt-insn-decoder.h
> create mode 100644 tools/perf/util/intel-pt-decoder/intel-pt-log.c
> create mode 100644 tools/perf/util/intel-pt-decoder/intel-pt-log.h
> create mode 100644 tools/perf/util/intel-pt-decoder/intel-pt-pkt-decoder.c
> create mode 100644 tools/perf/util/intel-pt-decoder/intel-pt-pkt-decoder.h
> create mode 100644 tools/perf/util/intel-pt.c
> create mode 100644 tools/perf/util/intel-pt.h

Yeah, so I did a 'newbie test':

I pulled the tree and saw that it has a tools/perf/Documentation/intel-bts.txt
file and started reading it.

Based on its text:

The Intel BTS kernel driver creates a new PMU for Intel BTS. The perf record
option is:

-e intel_bts//

Currently Intel BTS is limited to per-thread tracing so the --per-thread option
is also needed.

I tried the following command which failed:

triton:~/tip> perf record -e intel_bts// --per-thread sleep 1
invalid or unsupported event: 'intel_bts//'
Run 'perf list' for a list of valid events

usage: perf record [<options>] [<command>]
or: perf record [<options>] -- <command> [<options>]

-e, --event <event> event selector. use 'perf list' to list available events

That's a really ... unhelpful message. If I typoed something I want to know that.
If the kernel does not support something, I want to know about that too. Tooling
telling me: "maybe you typoed something, maybe it's not supported, I really don't
care" is not very productive.

So this was with a distro kernel, and in the hope that I'm missing some magic new
kernel feature, I tried it the latest -tip kernel, but it still gives me the same
failure.

So the test newbie user got stuck after wasting some time.

Me as a kernel developer could probably figure it out, but that's not the point:
if newbies cannot discover and use our new features then it's as if they didn't
exist, and I'm not pulling non-existent features! ;-)

Could we please improve all this?

Thanks,

Ingo