linux-kernel - Re: [PATCH] perf vendor events arm64: Remove uncountable events

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Message-ID: <CAP-5=fUNJLoy25rS=diSXNR9h-h4m6EFPTy8M+KpTKxm6HtDSA@mail.gmail.com>
Date: Fri, 2 Jan 2026 07:29:09 -0800
From: Ian Rogers <irogers@...gle.com>
To: James Clark <james.clark@...aro.org>
Cc: John Garry <john.g.garry@...cle.com>, Will Deacon <will@...nel.org>, 
	Mike Leach <mike.leach@...aro.org>, Leo Yan <leo.yan@...ux.dev>, 
	Peter Zijlstra <peterz@...radead.org>, Ingo Molnar <mingo@...hat.com>, 
	Arnaldo Carvalho de Melo <acme@...nel.org>, Namhyung Kim <namhyung@...nel.org>, 
	Mark Rutland <mark.rutland@....com>, 
	Alexander Shishkin <alexander.shishkin@...ux.intel.com>, Jiri Olsa <jolsa@...nel.org>, 
	Adrian Hunter <adrian.hunter@...el.com>, Akio Kakuno <fj3333bs@...jp.fujitsu.com>, 
	Yoshihiro Furudera <fj5100bi@...itsu.com>, linux-kernel@...r.kernel.org, 
	linux-arm-kernel@...ts.infradead.org, linux-perf-users@...r.kernel.org
Subject: Re: [PATCH] perf vendor events arm64: Remove uncountable events

On Wed, Dec 31, 2025 at 4:13 AM James Clark <james.clark@...aro.org> wrote:
>
> These events are never countable by the PMU and are only intended to
> be used as external inputs to trace. Therefore showing them in 'perf
> list' is misleading so remove them.

What does "trace" mean in this context?

Thanks,
Ian

> The generator script doesn't emit these events when used with the new
> telemetry-solution input files [1].
>
> 'perf list' should only show countable events because there are events
> that are sometimes implemented, sometimes countable and sometimes not,
> for example TRB_TRIG. If we always include any implemented events
> whether they are countable or not then it's not possible to tell whether
> they are usable in perf without going to the docs, defeating the point
> of 'perf list'.
>
> It's also not useful yet to display implemented events that are not
> countable (for help in using trace rather than perf stat), because
> PMU_OVFS and PMU_HOVFS are practically always implemented and TRB_TRIG
> is always implemented when there is TRBE.
>
> [1]: https://gitlab.arm.com/telemetry-solution/telemetry-solution/-/tree/main/data/pmu/cpu
>
> Signed-off-by: James Clark <james.clark@...aro.org>
> ---
>  tools/perf/pmu-events/arch/arm64/arm/cortex-a510/pmu.json  |  8 --------
>  tools/perf/pmu-events/arch/arm64/common-and-microarch.json | 12 ------------
>  tools/perf/pmu-events/arch/arm64/fujitsu/monaka/pmu.json   | 10 ----------
>  3 files changed, 30 deletions(-)
>
> diff --git a/tools/perf/pmu-events/arch/arm64/arm/cortex-a510/pmu.json b/tools/perf/pmu-events/arch/arm64/arm/cortex-a510/pmu.json
> deleted file mode 100644
> index d8b7b9f9e5fa..000000000000
> --- a/tools/perf/pmu-events/arch/arm64/arm/cortex-a510/pmu.json
> +++ /dev/null
> @@ -1,8 +0,0 @@
> -[
> -    {
> -        "ArchStdEvent": "PMU_OVFS"
> -    },
> -    {
> -        "ArchStdEvent": "PMU_HOVFS"
> -    }
> -]
> diff --git a/tools/perf/pmu-events/arch/arm64/common-and-microarch.json b/tools/perf/pmu-events/arch/arm64/common-and-microarch.json
> index 2416d9f8a83d..468cb085d879 100644
> --- a/tools/perf/pmu-events/arch/arm64/common-and-microarch.json
> +++ b/tools/perf/pmu-events/arch/arm64/common-and-microarch.json
> @@ -432,24 +432,12 @@
>          "EventName": "TRB_WRAP",
>          "BriefDescription": "Trace buffer current write pointer wrapped"
>      },
> -    {
> -        "PublicDescription": "PMU overflow, counters accessible to EL1 and EL0",
> -        "EventCode": "0x400D",
> -        "EventName": "PMU_OVFS",
> -        "BriefDescription": "PMU overflow, counters accessible to EL1 and EL0"
> -    },
>      {
>          "PublicDescription": "Trace buffer Trigger Event",
>          "EventCode": "0x400E",
>          "EventName": "TRB_TRIG",
>          "BriefDescription": "Trace buffer Trigger Event"
>      },
> -    {
> -        "PublicDescription": "PMU overflow, counters reserved for use by EL2",
> -        "EventCode": "0x400F",
> -        "EventName": "PMU_HOVFS",
> -        "BriefDescription": "PMU overflow, counters reserved for use by EL2"
> -    },
>      {
>          "PublicDescription": "PE Trace Unit external output 0",
>          "EventCode": "0x4010",
> diff --git a/tools/perf/pmu-events/arch/arm64/fujitsu/monaka/pmu.json b/tools/perf/pmu-events/arch/arm64/fujitsu/monaka/pmu.json
> deleted file mode 100644
> index 65bd6cdd0dd5..000000000000
> --- a/tools/perf/pmu-events/arch/arm64/fujitsu/monaka/pmu.json
> +++ /dev/null
> @@ -1,10 +0,0 @@
> -[
> -    {
> -        "ArchStdEvent": "PMU_OVFS",
> -        "BriefDescription": "This event counts the event generated each time one of the condition occurs described in Arm Architecture Reference Manual for A-profile architecture. This event is only for output to the trace unit."
> -    },
> -    {
> -        "ArchStdEvent": "PMU_HOVFS",
> -        "BriefDescription": "This event counts the event generated each time an event is counted by an event counter <n> and all of the condition occur described in Arm Architecture Reference Manual for A-profile architecture. This event is only for output to the trace unit."
> -    }
> -]
>
> ---
> base-commit: cbd41c6d4c26c161a2b0e70ad411d3885ff13507
> change-id: 20251230-james-perf-uncountable-events-28adfb93b73f
>
> Best regards,
> --
> James Clark <james.clark@...aro.org>
>