linux-kernel - Re: [PATCH v1] perf vendor power9 nest metrics: Correct unit from MB to MiB

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Message-ID: <a980f102-b468-4d55-abd6-885f02dc01e9@linux.ibm.com>
Date: Wed, 10 Dec 2025 11:09:40 +0530
From: Madhavan Srinivasan <maddy@...ux.ibm.com>
To: Ian Rogers <irogers@...gle.com>,
        Athira Rajeev <atrajeev@...ux.vnet.ibm.com>,
        Kajol Jain
 <kjain@...ux.ibm.com>,
        Peter Zijlstra <peterz@...radead.org>, Ingo Molnar <mingo@...hat.com>,
        Arnaldo Carvalho de Melo <acme@...nel.org>,
        Namhyung Kim <namhyung@...nel.org>,
        Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
        Jiri Olsa <jolsa@...nel.org>, Adrian Hunter <adrian.hunter@...el.com>,
        linux-perf-users@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v1] perf vendor power9 nest metrics: Correct unit from MB
 to MiB


On 10/31/25 9:56 PM, Ian Rogers wrote:
> 6.1e-5 is very close to 1/16384, where 16384 is 2^14, i.e. a power of
> 2. When units are in powers of 2 the IEC unit is MiB (mebibytes)
> rather than MB (megabytes) where the values are powers of 10. This
> patch corrects the unit for uniformity and because such units may be
> pattern matched against.


Changes looks fine to me.

Reviewed-by: Madhavan Srinivasan <maddy@...ux.ibm.com>
b/w  power10 metrics file could also have this fix I guess.

> Signed-off-by: Ian Rogers <irogers@...gle.com>
> ---
>   .../perf/pmu-events/arch/powerpc/power9/nest_metrics.json | 8 ++++----
>   1 file changed, 4 insertions(+), 4 deletions(-)
>
> diff --git a/tools/perf/pmu-events/arch/powerpc/power9/nest_metrics.json b/tools/perf/pmu-events/arch/powerpc/power9/nest_metrics.json
> index 7a5d1bf543f8..8d028a7c2777 100644
> --- a/tools/perf/pmu-events/arch/powerpc/power9/nest_metrics.json
> +++ b/tools/perf/pmu-events/arch/powerpc/power9/nest_metrics.json
> @@ -29,25 +29,25 @@
>   	"MetricExpr" : "nest_mcs01_imc@...MCS01_128B_RD_DISP_PORT01@ + nest_mcs01_imc@...MCS01_128B_RD_DISP_PORT23@",
>   	"MetricName" : "mcs01-read",
>   	"MetricGroup" : "memory-bandwidth",
> -	"ScaleUnit": "6.1e-5MB"
> +	"ScaleUnit": "6.1e-5MiB"
>       },
>       {
>   	"MetricExpr" : "nest_mcs23_imc@...MCS23_128B_RD_DISP_PORT01@ + nest_mcs23_imc@...MCS23_128B_RD_DISP_PORT23@",
>   	"MetricName" : "mcs23-read",
>   	"MetricGroup" : "memory-bandwidth",
> -	"ScaleUnit": "6.1e-5MB"
> +	"ScaleUnit": "6.1e-5MiB"
>       },
>       {
>   	"MetricExpr" : "nest_mcs01_imc@...MCS01_128B_WR_DISP_PORT01@ + nest_mcs01_imc@...MCS01_128B_WR_DISP_PORT23@",
>   	"MetricName" : "mcs01-write",
>   	"MetricGroup" : "memory-bandwidth",
> -	"ScaleUnit": "6.1e-5MB"
> +	"ScaleUnit": "6.1e-5MiB"
>       },
>       {
>   	"MetricExpr" : "nest_mcs23_imc@...MCS23_128B_WR_DISP_PORT01@ + nest_mcs23_imc@...MCS23_128B_WR_DISP_PORT23@",
>   	"MetricName" : "mcs23-write",
>   	"MetricGroup" : "memory-bandwidth",
> -	"ScaleUnit": "6.1e-5MB"
> +	"ScaleUnit": "6.1e-5MiB"
>       },
>       {
>   	"MetricExpr" : "nest_powerbus0_imc@...PB_CYC@",