linux-kernel - Re: perf script: Question: Python trace processing script contains the tid of the process in the common

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Date:   Wed, 5 Jul 2017 13:41:36 -0700
From:   Arun Kalyanasundaram <arunkaly@...gle.com>
To:     Arnaldo Carvalho de Melo <acme@...nel.org>
Cc:     Arnaldo Carvalho de Melo <acme@...hat.com>,
        Tom Zanussi <tzanussi@...il.com>, linux-kernel@...r.kernel.org,
        David Carrillo-Cisneros <davidcc@...gle.com>
Subject: Re: perf script: Question: Python trace processing script contains
 the tid of the process in the common_pid attribute

I wasn't entirely sure if we should modify the signature of the python
hooks_  as this would make existing scripts incompatible. So the patch
only adds sample->pid to the event_fields_dict param in
trace_unhandled().


On Wed, Jul 5, 2017 at 12:26 PM, Arnaldo Carvalho de Melo
<acme@...nel.org> wrote:
> Em Wed, Jul 05, 2017 at 04:25:45PM -0300, Arnaldo Carvalho de Melo escreveu:
>> Em Wed, Jul 05, 2017 at 09:22:07AM -0700, Arun Kalyanasundaram escreveu:
>> > Hi Arnaldo,
>> >
>> > Thank you for your reply.
>> > I actually meant tracepoint event handlers: def
>> > trace_unhandled(event_name, context, event_fields_dict)
>> > The dict parameter contains an attribute "common_pid" which is
>> > actually the "tid" of the thread. There are no other attributes that
>> > contain the actual pid of the process. So, I was wondering if this is
>> > something intentional? If not I can share a patch to fix this.
>>
>> Yeah there is a problem in:
>>
>> tools/perf/util/scripting-engines/trace-event-python.c
>>
>> static void python_process_event(union perf_event *event,
>>                                  struct perf_sample *sample,
>>                                  struct perf_evsel *evsel,
>>                                  struct addr_location *al)
>> {
>>         struct tables *tables = &tables_global;
>>
>>         switch (evsel->attr.type) {
>>         case PERF_TYPE_TRACEPOINT:
>>                 python_process_tracepoint(sample, evsel, al);
>>                 break;
>>         /* Reserve for future process_hw/sw/raw APIs */
>>         default:
>>                 if (tables->db_export_mode)
>>                         db_export__sample(&tables->dbe, event, sample, evsel, al);
>>                 else
>>                         python_process_general_event(sample, evsel, al);
>>         }
>> }
>>
>> The python_process_tracepoint() thing predates
>> python_process_general_event(), and doesn't adds the dict with all the
>> perf_sample entries that python_process_general_event() passes to the
>> python method :-\
>>
>> Both the per-tracepoint python hooks _and_ trace_unhandled() should get
>> that dict, is that what your patch does?
>
> Well, for performance reasons I think perhaps we could take a look at
> the signature of the python hook and provide the dictionary only if it
> is in it?
>
> - Arnaldo