linux-kernel - Re: [PATCH v5 2/6] perf vendor events arm64: Add TLB metrics for neoverse-n2

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Message-ID: <CAP-5=fVP_=FcEQChQwVpis9iyZsdb6NrVJQUo4GJA4_j=knfcA@mail.gmail.com>
Date:   Tue, 3 Jan 2023 09:14:01 -0800
From:   Ian Rogers <irogers@...gle.com>
To:     Jing Zhang <renyu.zj@...ux.alibaba.com>
Cc:     John Garry <john.g.garry@...cle.com>,
        Xing Zhengjun <zhengjun.xing@...ux.intel.com>,
        Will Deacon <will@...nel.org>,
        James Clark <james.clark@....com>,
        Mike Leach <mike.leach@...aro.org>,
        Leo Yan <leo.yan@...aro.org>,
        linux-arm-kernel@...ts.infradead.org,
        linux-perf-users@...r.kernel.org, linux-kernel@...r.kernel.org,
        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>,
        Andrew Kilroy <andrew.kilroy@....com>,
        Shuai Xue <xueshuai@...ux.alibaba.com>,
        Zhuo Song <zhuo.song@...ux.alibaba.com>
Subject: Re: [PATCH v5 2/6] perf vendor events arm64: Add TLB metrics for neoverse-n2

On Tue, Jan 3, 2023 at 3:39 AM Jing Zhang <renyu.zj@...ux.alibaba.com> wrote:
>
> Add TLB related metrics.
>
> Signed-off-by: Jing Zhang <renyu.zj@...ux.alibaba.com>
> Acked-by: Ian Rogers <irogers@...gle.com>
> ---
>  .../arch/arm64/arm/neoverse-n2/metrics.json        | 49 ++++++++++++++++++++++
>  1 file changed, 49 insertions(+)
>
> diff --git a/tools/perf/pmu-events/arch/arm64/arm/neoverse-n2/metrics.json b/tools/perf/pmu-events/arch/arm64/arm/neoverse-n2/metrics.json
> index c126f1bc..8a74e07 100644
> --- a/tools/perf/pmu-events/arch/arm64/arm/neoverse-n2/metrics.json
> +++ b/tools/perf/pmu-events/arch/arm64/arm/neoverse-n2/metrics.json
> @@ -26,5 +26,54 @@
>          "MetricGroup": "TopdownL1",
>          "MetricName": "backend_bound",
>          "ScaleUnit": "100%"
> +    },
> +    {
> +        "MetricExpr": "L1D_TLB_REFILL / L1D_TLB",
> +        "BriefDescription": "The rate of L1D TLB refill to the overall L1D TLB lookups",
> +        "MetricGroup": "TLB",
> +        "MetricName": "l1d_tlb_miss_rate",
> +        "ScaleUnit": "100%"
> +    },
> +    {
> +        "MetricExpr": "L1I_TLB_REFILL / L1I_TLB",
> +        "BriefDescription": "The rate of L1I TLB refill to the overall L1I TLB lookups",
> +        "MetricGroup": "TLB",
> +        "MetricName": "l1i_tlb_miss_rate",
> +        "ScaleUnit": "100%"
> +    },
> +    {
> +        "MetricExpr": "L2D_TLB_REFILL / L2D_TLB",
> +        "BriefDescription": "The rate of L2D TLB refill to the overall L2D TLB lookups",
> +        "MetricGroup": "TLB",
> +        "MetricName": "l2_tlb_miss_rate",
> +        "ScaleUnit": "100%"
> +    },
> +    {
> +        "MetricExpr": "DTLB_WALK / INST_RETIRED * 1000",
> +        "BriefDescription": "The rate of TLB Walks per kilo instructions for data accesses",
> +        "MetricGroup": "TLB",
> +        "MetricName": "dtlb_mpki",
> +        "ScaleUnit": "MPKI"
> +    },
> +    {
> +        "MetricExpr": "DTLB_WALK / L1D_TLB",
> +        "BriefDescription": "The rate of DTLB Walks to the overall L1D TLB lookups",
> +        "MetricGroup": "TLB",
> +        "MetricName": "dtlb_walk_rate",
> +        "ScaleUnit": "100%"
> +    },
> +    {
> +        "MetricExpr": "ITLB_WALK / INST_RETIRED * 1000",
> +        "BriefDescription": "The rate of TLB Walks per kilo instructions for instruction accesses",
> +        "MetricGroup": "TLB",
> +        "MetricName": "itlb_mpki",
> +        "ScaleUnit": "MPKI"

Did you test this? IIRC if there is no number in the ScaleUnit then
the scale factor becomes 0 and the metric value is always multiplied
by zero. Perhaps:

"MetricName": "itlb_miss_rate",
"MetricExpr": "ITLB / INST_RETIRED"
"ScaleUnit": "1000MPKI"

Thanks,
Ian

> +    },
> +    {
> +        "MetricExpr": "ITLB_WALK / L1I_TLB",
> +        "BriefDescription": "The rate of ITLB Walks to the overall L1I TLB lookups",
> +        "MetricGroup": "TLB",
> +        "MetricName": "itlb_walk_rate",
> +        "ScaleUnit": "100%"
>      }
>  ]
> --
> 1.8.3.1
>