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

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Message-ID: <Zr4kZTxgvD6bmi37@x1>
Date: Thu, 15 Aug 2024 12:53:09 -0300
From: Arnaldo Carvalho de Melo <acme@...nel.org>
To: James Clark <james.clark@...aro.org>
Cc: Thorsten Leemhuis <regressions@...mhuis.info>,
	Arnaldo Carvalho de Melo <acme@...hat.com>,
	Ian Rogers <irogers@...gle.com>,
	Mark Rutland <mark.rutland@....com>,
	Linux perf Profiling <linux-perf-users@...r.kernel.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	James Clark <james.clark@....com>,
	"cc: Marc Zyngier" <maz@...nel.org>,
	Hector Martin <marcan@...can.st>,
	Asahi Linux <asahi@...ts.linux.dev>,
	Linux regressions mailing list <regressions@...ts.linux.dev>
Subject: Re: [REGRESSION] Perf (userspace) broken on big.LITTLE systems since
 v6.5

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...)?