linux-kernel - Re: [PATCH v4 3/5] perf arch events: riscv arch std event files

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Date:   Fri, 24 Jun 2022 10:01:07 -0700
From:   Atish Patra <atishp@...shpatra.org>
To:     Nikita Shubin <nikita.shubin@...uefel.me>
Cc:     Anup Patel <anup@...infault.org>,
        João Mário Domingos 
        <joao.mario@...nico.ulisboa.pt>, linux <linux@...ro.com>,
        Nikita Shubin <n.shubin@...ro.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Ingo Molnar <mingo@...hat.com>,
        Arnaldo Carvalho de Melo <acme@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
        Jiri Olsa <jolsa@...nel.org>,
        Namhyung Kim <namhyung@...nel.org>,
        Paul Walmsley <paul.walmsley@...ive.com>,
        Palmer Dabbelt <palmer@...belt.com>,
        Albert Ou <aou@...s.berkeley.edu>,
        "linux-kernel@...r.kernel.org List" <linux-kernel@...r.kernel.org>,
        linux-perf-users@...r.kernel.org,
        linux-riscv <linux-riscv@...ts.infradead.org>
Subject: Re: [PATCH v4 3/5] perf arch events: riscv arch std event files

On Fri, Jun 24, 2022 at 9:01 AM Nikita Shubin <nikita.shubin@...uefel.me> wrote:
>
> From: Nikita Shubin <n.shubin@...ro.com>
>
> cycles, time and instret counters are defined by RISC-V privileged
> spec and they should be available on any RISC-V implementation, epose them
> to arch std event files, so they can be reused by particular PMU
> bindings.
>
> Derived-from-code-by: João Mário Domingos <joao.mario@...nico.ulisboa.pt>
> Signed-off-by: Nikita Shubin <n.shubin@...ro.com>

Why do we need this ? The PMU driver already parses the standard perf events.
So you can pass -e cycles -e instructions.

Even though time is described as a counter and accessibility
controlled by mcounteren, you can not start/stop it (no bit in
mcountinhibit).
Thus, it can't be used from perf.

> ---
>  .../pmu-events/arch/riscv/riscv-generic.json  | 20 +++++++++++++++++++
>  1 file changed, 20 insertions(+)
>  create mode 100644 tools/perf/pmu-events/arch/riscv/riscv-generic.json
>
> diff --git a/tools/perf/pmu-events/arch/riscv/riscv-generic.json b/tools/perf/pmu-events/arch/riscv/riscv-generic.json
> new file mode 100644
> index 000000000000..a7ffbe87a0f7
> --- /dev/null
> +++ b/tools/perf/pmu-events/arch/riscv/riscv-generic.json
> @@ -0,0 +1,20 @@
> +[
> +  {
> +    "PublicDescription": "CPU Cycles",
> +    "EventCode": "0x00",
> +    "EventName": "riscv_cycles",
> +    "BriefDescription": "CPU cycles RISC-V generic counter"
> +  },
> +  {
> +    "PublicDescription": "CPU Time",
> +    "EventCode": "0x01",
> +    "EventName": "riscv_time",
> +    "BriefDescription": "CPU time RISC-V generic counter"
> +  },
> +  {
> +    "PublicDescription": "CPU Instructions",
> +    "EventCode": "0x02",
> +    "EventName": "riscv_instret",
> +    "BriefDescription": "CPU retired instructions RISC-V generic counter"
> +  }
> +]
> --
> 2.35.1
>


-- 
Regards,
Atish