linux-kernel - Re: [PATCH v7 00/27] Legacy hardware/cache events as json

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Message-ID: <CAP-5=fX8ZV6WTmKcrrfPo0MUFiruJoWhYeUk3JrToEP=9-aPCA@mail.gmail.com>
Date: Wed, 15 Oct 2025 14:24:40 -0700
From: Ian Rogers <irogers@...gle.com>
To: James Clark <james.clark@...aro.org>
Cc: Namhyung Kim <namhyung@...nel.org>, Peter Zijlstra <peterz@...radead.org>, 
	Ingo Molnar <mingo@...hat.com>, Arnaldo Carvalho de Melo <acme@...nel.org>, 
	Alexander Shishkin <alexander.shishkin@...ux.intel.com>, Jiri Olsa <jolsa@...nel.org>, 
	Adrian Hunter <adrian.hunter@...el.com>, Xu Yang <xu.yang_2@....com>, 
	Thomas Falcon <thomas.falcon@...el.com>, Andi Kleen <ak@...ux.intel.com>, 
	linux-kernel@...r.kernel.org, linux-perf-users@...r.kernel.org, 
	Atish Patra <atishp@...osinc.com>, Beeman Strong <beeman@...osinc.com>, Leo Yan <leo.yan@....com>, 
	Vince Weaver <vincent.weaver@...ne.edu>
Subject: Re: [PATCH v7 00/27] Legacy hardware/cache events as json

On Wed, Oct 15, 2025 at 10:39 AM James Clark <james.clark@...aro.org> wrote:
>
>
>
> On 15/10/2025 4:53 pm, Namhyung Kim wrote:
> > On Sun, 05 Oct 2025 11:24:03 -0700, Ian Rogers wrote:
> >
> >> Mirroring similar work for software events in commit 6e9fa4131abb
> >> ("perf parse-events: Remove non-json software events"). These changes
> >> migrate the legacy hardware and cache events to json.  With no hard
> >> coded legacy hardware or cache events the wild card, case
> >> insensitivity, etc. is consistent for events. This does, however, mean
> >> events like cycles will wild card against all PMUs. A change doing the
> >> same was originally posted and merged from:
> >> https://lore.kernel.org/r/20240416061533.921723-10-irogers@google.com
> >> and reverted by Linus in commit 4f1b067359ac ("Revert "perf
> >> parse-events: Prefer sysfs/JSON hardware events over legacy"") due to
> >> his dislike for the cycles behavior on ARM with perf record. Earlier
> >> patches in this series make perf record event opening failures
> >> non-fatal and hide the cycles event's failure to open on ARM in perf
> >> record, so it is expected the behavior will now be transparent in perf
> >> record on ARM. perf stat with a cycles event will wildcard open the
> >> event on all PMUs, however, with default events the cycles event will
> >> only be opened on core PMUs.
> >>
> >> [...]
> >
> > Applied to perf-tools-next, thanks!
> >
> > Best regards,
> > Namhyung
> >
>
> Hi Namhyung,
>
> I'm still getting the build failure that I mentioned on patch 5. This
> only seems to happen with out of source builds:
>
>    $ make -C tools/perf O=../build/local/ V=1
>
>
>    static const struct pmu_sys_events pmu_sys_event_tables[] = {
>          {
> -               .event_table = {
> -                       .pmus = pmu_events__test_soc_sys,
> -                       .num_pmus = ARRAY_SIZE(pmu_events__test_soc_sys)
> -               },
> -               .name = "pmu_events__test_soc_sys",
> -       },
> -       {
>                  .event_table = { 0, 0 },
>                  .metric_table = { 0, 0 },
>          },
> make[3]: *** [pmu-events/Build:54:
> /home/james/workspace/linux/build/local/pmu-events/empty-pmu-events.log]
> Error 1

Sorry for the issue. Is this happening when you don't do a clean
first? I tried recreating your output path, but I can't reproduce the
issue on a clean build. The diff above indicates some issue with the
Makefile processing tools/perf/pmu-events/arch/test/test_soc/. This
directory should be copied to
../build/local/pmu-events/arch/test/test_soc/ and so I wonder if the
copy failed for some reason.

The copy rule is:
https://web.git.kernel.org/pub/scm/linux/kernel/git/perf/perf-tools-next.git/tree/tools/perf/pmu-events/Build?h=perf-tools-next#n33
```
# Copy checked-in json for generation.
$(OUTPUT)pmu-events/arch/%: pmu-events/arch/%
$(call rule_mkdir)
$(Q)$(call echo-cmd,gen)cp $< $@
```

The mapping of file names happens in the patsubst in:
https://web.git.kernel.org/pub/scm/linux/kernel/git/perf/perf-tools-next.git/tree/tools/perf/pmu-events/Build?h=perf-tools-next#n42
```
GEN_JSON = $(patsubst %,$(OUTPUT)%,$(JSON)) $(LEGACY_CACHE_JSON)
```

Those files are dependencies for the empty-pmu-events.c test so I'm
not sure how this can be failing for you.

Thanks,
Ian