linux-kernel - Re: [PATCH v3 2/6] scripts: python: Extact necessary information from process event

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Date:   Mon, 17 Jul 2023 21:01:53 +0530
From:   Anup Sharma <anupnewsmail@...il.com>
To:     Ian Rogers <irogers@...gle.com>
Cc:     Anup Sharma <anupnewsmail@...il.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Ingo Molnar <mingo@...hat.com>,
        Arnaldo Carvalho de Melo <acme@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
        Jiri Olsa <jolsa@...nel.org>,
        Namhyung Kim <namhyung@...nel.org>,
        Adrian Hunter <adrian.hunter@...el.com>,
        linux-perf-users@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3 2/6] scripts: python: Extact necessary information
 from process event

On Wed, Jul 12, 2023 at 10:03:57AM -0700, Ian Rogers wrote:
> On Wed, Jul 12, 2023 at 10:01 AM Ian Rogers <irogers@...gle.com> wrote:
> >
> > On Mon, Jul 10, 2023 at 4:10 PM Anup Sharma <anupnewsmail@...il.com> wrote:
> > >
> > > The script takes in a sample event dictionary(param_dict) and retrieves
> > > relevant data such as time stamp, PID, TID, thread name. Also start time
> > > is defined.
> > >
> > > Signed-off-by: Anup Sharma <anupnewsmail@...il.com>
> > > ---
> > >  .../perf/scripts/python/firefox-gecko-converter.py  | 13 ++++++++++++-
> > >  1 file changed, 12 insertions(+), 1 deletion(-)
> > >
> > > diff --git a/tools/perf/scripts/python/firefox-gecko-converter.py b/tools/perf/scripts/python/firefox-gecko-converter.py
> > > index 5b342641925c..765f1775cee5 100644
> > > --- a/tools/perf/scripts/python/firefox-gecko-converter.py
> > > +++ b/tools/perf/scripts/python/firefox-gecko-converter.py
> > > @@ -21,8 +21,19 @@ sys.path.append(os.environ['PERF_EXEC_PATH'] + \
> > >  from perf_trace_context import *
> > >  from Core import *
> > >
> >
> > It'd be nice to have a comment here, perhaps:
> > # The time stamp from the first of the time ordered events.
> >

Sure. I will add it.

> > > +start_time = None
> > > +
> > >  def trace_end():
> > >         pass
> > >
> > >  def process_event(param_dict):
> > > -       pass
> > > +       global start_time
> > > +       # Extract relevant information from the event parameters. The event parameters
> > > +       # are in a dictionary:
> > > +       time_stamp = (param_dict['sample']['time'] // 1000) / 1000
> > > +       pid = param_dict['sample']['pid']
> > > +       tid = param_dict['sample']['tid']
> > > +       thread_name = param_dict['comm']
> > > +
> > > +       # Assume that start time is the time of the first event.
> > > +       start_time = time_stamp if not start_time else start_time
> >
> > I appreciate that this is one line, but it takes some getting your
> > head around that start_time is being assigned to itself in the common
> > case. I think this would be more readable as:
> >
> > if not start_time:
> >   start_time = time_stamp

Sure. I will change it.

> I believe the events are guaranteed time ordered in perf script. The
> ordered_event logic handles this, but I likely haven't got a full
> grasp on all the corners of it. You can always assert the behavior
> (comments with guarantees :-) ):
> 
> assert start_time <= time_stamp, "Events aren't time ordered"

I dont think assert is usefull here as start_time will be initialized
and assigned only once for all the process event triggers. So, the
significance of assert is not clear to me.

> Thanks,
> Ian
> 
> > Thanks,
> > Ian
> >
> > > --
> > > 2.34.1
> > >