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From: Ian Rogers <irogers@google.com>
Date: Wed, 29 May 2024 11:18:16 -0700
Message-ID: <CAP-5=fXxsFp9tynNhkYqrgCMtP4F-XaADz+06hTWHHFVpVhfDg@mail.gmail.com>
Subject: Re: [PATCH v3 3/5] perf stat: Remove evlist__add_default_attrs use strings
To: James Clark <james.clark@arm.com>
Cc: Peter Zijlstra <peterz@infradead.org>, Ingo Molnar <mingo@redhat.com>, 
	Arnaldo Carvalho de Melo <acme@kernel.org>, Namhyung Kim <namhyung@kernel.org>, 
	Mark Rutland <mark.rutland@arm.com>, 
	Alexander Shishkin <alexander.shishkin@linux.intel.com>, Jiri Olsa <jolsa@kernel.org>, 
	Adrian Hunter <adrian.hunter@intel.com>, Kan Liang <kan.liang@linux.intel.com>, 
	Ravi Bangoria <ravi.bangoria@amd.com>, Yang Jihong <yangjihong@bytedance.com>, 
	Ze Gao <zegao2021@gmail.com>, Leo Yan <leo.yan@linux.dev>, Song Liu <song@kernel.org>, 
	K Prateek Nayak <kprateek.nayak@amd.com>, Kaige Ye <ye@kaige.org>, 
	Yicong Yang <yangyicong@hisilicon.com>, linux-perf-users@vger.kernel.org, 
	linux-kernel@vger.kernel.org
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On Wed, May 29, 2024 at 10:39=E2=80=AFAM Ian Rogers <irogers@google.com> wr=
ote:
>
> On Wed, May 29, 2024 at 8:39=E2=80=AFAM James Clark <james.clark@arm.com>=
 wrote:
> >
> >
> >
> > On 10/05/2024 06:37, Ian Rogers wrote:
> > > add_default_atttributes would add evsels by having pre-created
> > > perf_event_attr, however, this needed fixing for hybrid as the
> > > extended PMU type was necessary for each core PMU. The logic for this
> > > was in an arch specific x86 function and wasn't present for ARM,
> > > meaning that default events weren't being opened on all PMUs on
> > > ARM. Change the creation of the default events to use parse_events an=
d
> > > strings as that will open the events on all PMUs.
> > >
> > > Rather than try to detect events on PMUs before parsing, parse the
> > > event but skip its output in stat-display.
> > >
> > > The previous order of hardware events was: cycles,
> > > stalled-cycles-frontend, stalled-cycles-backend, instructions. As
> > > instructions is a more fundamental concept the order is changed to:
> > > instructions, cycles, stalled-cycles-frontend, stalled-cycles-backend=
.
> > >
> > > Closes: https://lore.kernel.org/lkml/CAP-5=3DfVABSBZnsmtRn1uF-k-G1GWM=
-L5SgiinhPTfHbQsKXb_g@mail.gmail.com/
> >
> > Taking a look at this one now. I think some example commands and output=
s
> > in the commit message would be helpful because there are quite a few
> > different things mentioned in the closes link.
> >
> > But I'm assuming this is just for the command without specifying an eve=
nt:
> >
> >   $ perf stat
> >
> > I didn't realise that wasn't working properly and I'd missed that Mark
> > spotted it in that link.
>
> Hi James,
>
> Do you want to take on owning fixing this? My concern is that by using
> event parsing:
>
> +                               "context-switches,"
> +                               "cpu-migrations,"
> +                               "page-faults,"
> +                               "instructions,"
> +                               "cycles,"
> +                               "stalled-cycles-frontend,"
> +                               "stalled-cycles-backend,"
> +                               "branches,"
> +                               "branch-misses",
>
> any of the names could conflict with something advertised on an ARM
> PMU somewhere. Clearly cycles has already proved to be controversial
> and broken for perf record on Neoverse.

Oh and these events are also broken on ARM M? PMUs with the revert
that's in v6.10, so I don't know how to go about fixing this.

Thanks,
Ian