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

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Message-ID: <aUGkvNzhls6cE39T@x1>
Date: Tue, 16 Dec 2025 15:28:12 -0300
From: Arnaldo Carvalho de Melo <acme@...nel.org>
To: Madhavan Srinivasan <maddy@...ux.ibm.com>
Cc: 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>, 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 Wed, Dec 10, 2025 at 11:09:40AM +0530, Madhavan Srinivasan wrote:
> 
> 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.

Thanks, applied to perf-tools-next,

- Arnaldo
 
> > 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@",