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From: Ian Rogers <irogers@google.com>
Date: Wed, 10 Jan 2024 08:29:18 -0800
Message-ID: <CAP-5=fWCn88KchSdQg87FRY0cpH4tVqO0UEYMhE=ioANeRBdwg@mail.gmail.com>
Subject: Re: perf test hybrid failing on 14700K
To: Mark Rutland <mark.rutland@arm.com>
Cc: "Liang, Kan" <kan.liang@linux.intel.com>, Arnaldo Carvalho de Melo <acme@kernel.org>, 
	Kan Liang <kan.liang@intel.com>, Adrian Hunter <adrian.hunter@intel.com>, 
	Jiri Olsa <jolsa@kernel.org>, Namhyung Kim <namhyung@kernel.org>, linux-perf-users@vger.kernel.org, 
	Linux Kernel Mailing List <linux-kernel@vger.kernel.org>
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On Tue, Jan 9, 2024 at 8:37=E2=80=AFAM Mark Rutland <mark.rutland@arm.com> =
wrote:
>
> On Fri, Jan 05, 2024 at 09:21:21AM -0800, Ian Rogers wrote:
> > While much has been done in the perf tool to work around latent issues
> > with ARM's PMU drivers and the behavior changes they have instigated,
> > except for 5c816728651a ("arm_pmu: Add PERF_PMU_CAP_EXTENDED_HW_TYPE
> > capability") where I wrote the original version, there doesn't seem to
> > have been progress made on the ARM PMU driver nor on ARM testing -
> > which was why such an issue could exist for so long, across numerous
> > Linux releases and ultimately break Hector and Martin.
>
> Ian, which latent issues in the PMU drivers are you referring to?

Core PMUs generally have a lookup from legacy to non-legacy event,
from the past discussion this was missing on the problematic PMUs
hence the sysfs versions.

> I already pointed out that one of the problems you have claimed to be a d=
river
> bug is actually due to userspace incorrectly detecting support for the ex=
tended
> HW type, and I suggested some options which you have so far ignored:
>
>   https://lore.kernel.org/lkml/ZV-CUlQhlkdOzfFZ@FVFF77S0Q05N.cambridge.ar=
m.com/
>   https://lore.kernel.org/lkml/ZV-ItX1eMeIdo_00@FVFF77S0Q05N.cambridge.ar=
m.com/

Those suggestions look fine but you seemed to be suggesting testing.
Lacking hardware with the broken PMU(s) I'm not able to do this. Could
you turn the suggestion into a patch and test on BIG.little? I can
test on Intel Alderlake.

Thanks,
Ian

> I agree that testing is a problem, and we need to do better from the arm =
side.
>
> Thanks,
> Mark.