linux-kernel - Re: [PATCH v2 11/11] perf python tracepoint: Switch to using parse

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Message-ID: <Z9Do_ZSHuuZde4eZ@google.com>
Date: Tue, 11 Mar 2025 18:53:01 -0700
From: Namhyung Kim <namhyung@...nel.org>
To: Ian Rogers <irogers@...gle.com>
Cc: 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>,
	Adrian Hunter <adrian.hunter@...el.com>,
	Kan Liang <kan.liang@...ux.intel.com>,
	Yicong Yang <yangyicong@...ilicon.com>,
	James Clark <james.clark@...aro.org>,
	"Dr. David Alan Gilbert" <linux@...blig.org>,
	Levi Yun <yeoreum.yun@....com>, Ze Gao <zegao2021@...il.com>,
	Weilin Wang <weilin.wang@...el.com>, Xu Yang <xu.yang_2@....com>,
	linux-perf-users@...r.kernel.org, linux-kernel@...r.kernel.org,
	Howard Chu <howardchu95@...il.com>
Subject: Re: [PATCH v2 11/11] perf python tracepoint: Switch to using
 parse_events

On Mon, Mar 10, 2025 at 04:40:36PM -0700, Ian Rogers wrote:
> On Mon, Mar 10, 2025 at 3:17 PM Namhyung Kim <namhyung@...nel.org> wrote:
> >
> > On Fri, Feb 28, 2025 at 02:23:08PM -0800, Ian Rogers wrote:
> > > Rather than manually configuring an evsel, switch to using
> > > parse_events for greater commonality with the rest of the perf code.
> > >
> > > Reviewed-by: Howard Chu <howardchu95@...il.com>
> > > Signed-off-by: Ian Rogers <irogers@...gle.com>
> > > ---
> > >  tools/perf/python/tracepoint.py | 23 +++++++++++------------
> > >  1 file changed, 11 insertions(+), 12 deletions(-)
> > >
> > > diff --git a/tools/perf/python/tracepoint.py b/tools/perf/python/tracepoint.py
> > > index bba68a6d4515..38b2b6d11f64 100755
> > > --- a/tools/perf/python/tracepoint.py
> > > +++ b/tools/perf/python/tracepoint.py
> > > @@ -5,24 +5,23 @@
> > >
> > >  import perf
> > >
> > > -class tracepoint(perf.evsel):
> > > -    def __init__(self, sys, name):
> > > -        config = perf.tracepoint(sys, name)
> > > -        perf.evsel.__init__(self,
> > > -                            type   = perf.TYPE_TRACEPOINT,
> > > -                            config = config,
> > > -                            freq = 0, sample_period = 1, wakeup_events = 1,
> > > -                            sample_type = perf.SAMPLE_PERIOD | perf.SAMPLE_TID | perf.SAMPLE_CPU | perf.SAMPLE_RAW | perf.SAMPLE_TIME)
> > > -
> > >  def main():
> > > -    tp      = tracepoint("sched", "sched_switch")
> > >      cpus    = perf.cpu_map()
> > >      threads = perf.thread_map(-1)
> > > +    evlist = perf.parse_events("sched:sched_switch", cpus, threads)
> > > +    # Disable tracking of mmaps and similar that are unnecessary.
> > > +    for ev in evlist:
> > > +        ev.tracking = False
> > > +    # Configure evsels with default record options.
> > > +    evlist.config()
> >
> > I think the default option uses frequency of 4000 but tracepoints want
> > to use period of 1.  Also I'm not sure if it sets the proper sample type
> > bits namely PERF_SAMPLE_RAW.
> 
> I used trace to ensure they matched. Fwiw, the sample_period for a
> tracepoint is set to 1 in evsel__newtp_idx:
> https://web.git.kernel.org/pub/scm/linux/kernel/git/perf/perf-tools-next.git/tree/tools/perf/util/evsel.c?h=perf-tools-next#n621
> and the evsel__config won't overwrite an already set sample_period:
> https://web.git.kernel.org/pub/scm/linux/kernel/git/perf/perf-tools-next.git/tree/tools/perf/util/evsel.c?h=perf-tools-next#n1341

Ok, it only sets the default value and it will use the attr from
evsel__newtp_idx().  Thanks for checking this.

Thanks,
Namhyung

> >
> >
> > > +    # Simplify the sample_type and read_format of evsels
> > > +    for ev in evlist:
> > > +        ev.sample_type = ev.sample_type & ~perf.SAMPLE_IP
> > > +        ev.read_format = 0
> > >
> > > -    evlist = perf.evlist(cpus, threads)
> > > -    evlist.add(tp)
> > >      evlist.open()
> > >      evlist.mmap()
> > > +    evlist.enable();
> > >
> > >      while True:
> > >          evlist.poll(timeout = -1)
> > > --
> > > 2.48.1.711.g2feabab25a-goog
> > >