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SubjectRe: [REGRESSION] Perf (userspace) broken on big.LITTLE systems since v6.5
On Tue, Nov 21, 2023 at 09:08:48PM +0900, Hector Martin wrote:
> Perf broke on all Apple ARM64 systems (tested almost everything), and
> according to maz also on Juno (so, probably all big.LITTLE) since v6.5.
>
> Test command:
>
> sudo taskset -c 0 ./perf stat -e apple_icestorm_pmu/cycles/ -e
> apple_firestorm_pmu/cycles/ -e cycles ls
>
> Since this is taskset to CPU #0 (LITTLE core, icestorm), only events for
> icestorm are expected.
>
> I bisected the breakage to two distinct points:
>
> 5ea8f2ccffb is the first bad commit. With its parent, the output is as
> expected (same as v6.4):
>
> 3,297,462 apple_icestorm_pmu/cycles/
>
> <not counted> apple_firestorm_pmu/cycles/
> (0.00%)
> <not counted> cycles
> (0.00%)
>
> With 5ea8f2ccffb everything breaks:
>
> <not supported> apple_icestorm_pmu/cycles/
>
> <not supported> apple_firestorm_pmu/cycles/
>
> <not counted> cycles
> (0.00%)
>
> Somewhere along the way to 82fe2e45cdb00 things get even worse (didn't
> bother bisecting this range). With its parent:
>
> <not supported> apple_icestorm_pmu/cycles/
>
> <not supported> apple_firestorm_pmu/cycles/
>
> <not supported> apple_icestorm_pmu/cycles/
>
> <not supported> apple_firestorm_pmu/cycles/
>
> Then 82fe2e45cdb00 leads to the current v6.5 behavior:
>
> <not counted> apple_icestorm_pmu/cycles/
> (0.00%)
> <not counted> apple_firestorm_pmu/cycles/
> (0.00%)
> <not counted> cycles
> (0.00%)
>
> If I taskset the task to CPU#2 (big core, firestorm), I get events:
>
> 1,454,858 apple_icestorm_pmu/cycles/
>
> 1,454,760 apple_firestorm_pmu/cycles/
>
> 1,454,384 cycles
>
>
> So the current behavior is that all output seems to come from the
> firestorm PMU event counter, regardless of requested event.
>
> This is all unchanged and still broken in v6.7-rc2.
>

Thanks for the regression report (and it has been handled well already).
I'm adding it to regzbot for tracking:

#regzbot ^introduced: 5ea8f2ccffb239

--
An old man doll... just what I always wanted! - Clara
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