linux-kernel - Re: [PATCH v2 4/7] scripts: python: implement get or create stack function

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Date:   Tue, 11 Jul 2023 03:31:10 +0530
From:   Anup Sharma <anupnewsmail@...il.com>
To:     Namhyung Kim <namhyung@...nel.org>
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>, Ian Rogers <irogers@...gle.com>,
        Adrian Hunter <adrian.hunter@...el.com>,
        linux-perf-users@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 4/7] scripts: python: implement get or create stack
 function

On Wed, Jul 05, 2023 at 10:55:52PM -0700, Namhyung Kim wrote:
> On Wed, Jul 5, 2023 at 12:48 PM Anup Sharma <anupnewsmail@...il.com> wrote:
> >
> > The get_or_create_stack function is responsible for retrieving
> > or creating a stack based on the provided frame and prefix.
> > It first generates a key using the frame and prefix values.
> > If the stack corresponding to the key is found in the stackMap,
> > it is returned. Otherwise, a new stack is created by appending
> > the prefix and frame to the stackTable's 'data' array. The key
> > and the index of the newly created stack are added to the
> > stackMap for future reference.
> >
> > Signed-off-by: Anup Sharma <anupnewsmail@...il.com>
> > ---
> >  tools/perf/scripts/python/firefox-gecko-converter.py | 11 +++++++++++
> >  1 file changed, 11 insertions(+)
> >
> > diff --git a/tools/perf/scripts/python/firefox-gecko-converter.py b/tools/perf/scripts/python/firefox-gecko-converter.py
> > index e56864e78dc1..6f69c083d3ff 100644
> > --- a/tools/perf/scripts/python/firefox-gecko-converter.py
> > +++ b/tools/perf/scripts/python/firefox-gecko-converter.py
> > @@ -65,6 +65,17 @@ def process_event(param_dict):
> >                         },
> >                         'data': [],
> >                 }
> > +               stringTable = []
> > +
> > +               stackMap = dict()
> > +               def get_or_create_stack(frame, prefix):
> > +                       key = f"{frame}" if prefix is None else f"{frame},{prefix}"
> > +                       stack = stackMap.get(key)
> 
> I'm confused about what the 'stack' is.

The stack is a list of frames.

> > +                       if stack is None:
> > +                               stack = len(stackTable['data'])
> 
> It seems like a kind of index for the stackTable's data.

Yes, it is an index.

> > +                               stackTable['data'].append([prefix, frame])
> > +                               stackMap[key] = stack
> > +                       return stack
> 
> So this function returns an index, right?

Correct, it returns an index. This index allows to access or identify
a specific stack within the table.

> Thanks,
> Namhyung
> 
> 
> >
> >         def _addThreadSample(pid, tid, threadName, time_stamp, stack):
> >                 thread = thread_map.get(tid)
> > --
> > 2.34.1
> >