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 16:26:40 -0300
From:   Arnaldo Carvalho de Melo <acme@...nel.org>
To:     Arun Kalyanasundaram <arunkaly@...gle.com>
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

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