Re: [REGRESSION] Perf (userspace) broken on big.LITTLE systems since v6.5

[Arnaldo Carvalho de Melo <acme@kernel.org>]

On Thu, Aug 15, 2024 at 12:27:21PM -0300, Arnaldo Carvalho de Melo wrote:
> On Thu, Aug 15, 2024 at 04:15:41PM +0100, James Clark wrote:
> > In one of your investigations here
> > https://lore.kernel.org/lkml/Zld3dlJHjFMFG02v@x1/ comparing "cycles",
> > "cpu-cycles" and "cpu_cycles" events on Arm you say only some of them open
> > events on both core types. I wasn't able to reproduce that on
> > perf-tools-next (27ac597c0e) or v6.9 (a38297e3fb) for perf record or stat. I
> > guessed the 6.9 tag because you only mentioned it was on tip and it was 29th
> > May. For me they all open exactly the same two legacy events with the
> > extended type ID set.
> > 
> > It looks like the behavior you see would be caused by either missing this
> > kernel change:
> > 
> >   5c81672865 ("arm_pmu: Add PERF_PMU_CAP_EXTENDED_HW_TYPE capability")
> >    (v6.6 release)

What I have now is:

6.1.92-15907-gf36fd2695db3

It was a bit older, but 6.1 ish as well, I'll try to either get a new
kernel from Libre Computer or build one myself.

- Arnaldo

> > Or this userspace change, but unlikely as it was a fix for Apple M hardware:
> > 
> >   25412c036 ("perf print-events: make is_event_supported() more robust")
> >    (v6.9 release)
> > 
> > Do you remember if you were using a new kernel or only testing a new Perf?
> 
> I normally use the distro/SoC provided kernel, didn't I add the 'uname
> -a' output in those investigations (/me slaps himself in the face
> speculatively...)?