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

Adrian Hunter
2015-06-30T07:57:00Z

On 30/06/15 07:58, Ingo Molnar wrote:
>
> * 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.

That is not entirely true. The message says "Run 'perf list' for a list of
valid events" which will tell you if the event is valid. So you can tell the
difference between a typo and unsupported event.

>
> 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?

'perf list' shows the event wasn't supported, so I am not sure what more the
"newbie" could expect. Do you have any suggestions?