Re: perf test hybrid failing on 14700K

[Ian Rogers]

On Tue, Jan 9, 2024 at 8:37 AM Mark Rutland <mark.rutland@xxxxxxx> 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 driver
> bug is actually due to userspace incorrectly detecting support for the extended
> HW type, and I suggested some options which you have so far ignored:
>
>   https://lore.kernel.org/lkml/ZV-CUlQhlkdOzfFZ@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxx/
>   https://lore.kernel.org/lkml/ZV-ItX1eMeIdo_00@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxx/

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.