Re: [RFC] perf tools: Update JSON event description

[Namhyung Kim <namhyung@kernel.org>]

On Wed, Oct 29, 2025 at 08:28:34AM -0700, Ian Rogers wrote:
> On Mon, Oct 27, 2025 at 11:58 AM Namhyung Kim <namhyung@kernel.org> wrote:
> >
> > Hi Ian,
> >
> > I'm trying to make this change in the JSON description for hardware and
> > software events.  But I got a build failure in the empty-pmu-events.c
> > even after I re-generated it like below.
> >
> >   cd pmu-events
> >   ./jevents.py none none $PWD empty-pmu-events.c
> >
> > Did I miss something?
> 
> So the build failure/diff has the path to the generated
> empty-pmu-events.c. I'd copy that file rather than try to recreate the

I see.

> command line - although there should be no reason generating the
> command line fails it looks to me that you need to pass "$PWD/arch"
> rather than "$PWD":
> https://web.git.kernel.org/pub/scm/linux/kernel/git/perf/perf-tools-next.git/tree/tools/perf/pmu-events/Build?h=tmp.perf-tools-next#n51
> Fwiw, the formatting in legacy-hardware.json was based on Intel doing
> the same thing and not wanting to start new conventions:
> https://web.git.kernel.org/pub/scm/linux/kernel/git/perf/perf-tools-next.git/tree/tools/perf/pmu-events/arch/x86/skylakex/pipeline.json?h=tmp.perf-tools-next#n32
> ```
>     {
>         "BriefDescription": "Conditional branch instructions retired.
> [This event is alias to BR_INST_RETIRED.CONDITIONAL]",
>         "Counter": "0,1,2,3",
>         "Errata": "SKL091",
>         "EventCode": "0xC4",
>         "EventName": "BR_INST_RETIRED.COND",
>         "PublicDescription": "This event counts conditional branch
> instructions retired. [This event is alias to
> BR_INST_RETIRED.CONDITIONAL]",
>         "SampleAfterValue": "400009",
>         "UMask": "0x1"
>     },
>     {
>         "BriefDescription": "Conditional branch instructions retired.
> [This event is alias to BR_INST_RETIRED.COND]",
>         "Counter": "0,1,2,3",
>         "Errata": "SKL091",
>         "EventCode": "0xC4",
>         "EventName": "BR_INST_RETIRED.CONDITIONAL",
>         "PEBS": "1",
>         "PublicDescription": "This event counts conditional branch
> instructions retired. [This event is alias to BR_INST_RETIRED.COND]",
>         "SampleAfterValue": "400009",
>         "UMask": "0x1"
>     },
> ```
> As the order of seeing events isn't well defined, I'm not sure what we
> gain by shorter descriptions and it could be frustrating for a user to
> see that 'cycles' definition is in effect a redirection.

I generally prefer short and clear descriptions and feel better to
remove duplications.  But I don't want to change the vendor JSON and
this change is not important so I can drop it.

Thanks,
Namhyung