linux-kernel - RE: [PATCH] Remove some PMU events for FUJITSU-MONAKA

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Message-ID:
 <OS3PR01MB690377379ED81FDF8D60142DD4D52@OS3PR01MB6903.jpnprd01.prod.outlook.com>
Date: Fri, 7 Mar 2025 03:10:47 +0000
From: "Yoshihiro Furudera (Fujitsu)" <fj5100bi@...itsu.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>, 'Ian
 Rogers' <irogers@...gle.com>, 'Adrian Hunter' <adrian.hunter@...el.com>,
	"'Liang, Kan'" <kan.liang@...ux.intel.com>,
	"'linux-arm-kernel@...ts.infradead.org'"
	<linux-arm-kernel@...ts.infradead.org>, "'linux-perf-users@...r.kernel.org'"
	<linux-perf-users@...r.kernel.org>, "'linux-kernel@...r.kernel.org'"
	<linux-kernel@...r.kernel.org>, "Akio Kakuno (Fujitsu)"
	<fj3333bs@...itsu.com>
Subject: RE: [PATCH] Remove some PMU events for FUJITSU-MONAKA

Hi, James
Thank you for your comment.

> On 05/03/2025 6:40 am, Yoshihiro Furudera (Fujitsu) wrote:
> > Hi, James
> >
> >>
> >> Hi, James
> >> Thank you for your comment.
> >>
> >>> On 27/02/2025 5:40 am, Yoshihiro Furudera wrote:
> >>>> The following events are not counted properly:
> >>>>
> >>>> 0x0037 LL_CACHE_MISS_RD
> >>>> 0x400B L3D_CACHE_LMISS_RD
> >>>
> >>> These two are discoverable so will still appear in
> >>> /sys/bus/event_source/devices/armv8_pmuv3_0/events/ if the hardware
> >>> says they exist. It might be better to change the json strings of
> >>> these two to warn that they don't work if that's the case, otherwise
> >>> Perf will still list them and you'll be worse off.
> >>
> >> I will leave these 2 events and
> >> add a warning message to the description in the JSON file.
> >> I will handle other events in the same way as these 2 events.
> >
> > I'm thinking of adding one of the following warnings to the
> > description of events where inaccurate counts occur on FUJITSU-MONAKA.
> > Is this okay?
> >
> > 1.Simple version
> > "Note: This event does not count accurately."
> >
> > 2.Detailed version
> > "Note: This event does not count accurately because it counts as a miss
> regardless of whether the L3 prefetch is a hit or miss."
> >
> > I think "2.Detailed version" is better.
> >
> > example:
> > {
> >      "EventCode": "0x0396",
> >      "EventName": "L2D_CACHE_REFILL_L3D_MISS",
> >      "BriefDescription": "This event counts operations that cause a miss of the
> L3 cache. Note: This event does not count accurately because it counts as a miss
> regardless of whether the L3 prefetch is a hit or miss."
> > }
> >
> > Best Regards,
> > Yoshihiro Furudera
> 
> You could have both by using BriefDescription and PublicDescription. The longer
> one being available with 'perf list -v'. I think that's what that feature is for.

Thank you for your suggestion.
After discussing this with the OS team,
we would like to move forward with the policy of
defining "2.Detailed version" in the Brief Description.
Please let me make a final decision after discussing it
with the hardware team.

> 
> Either way you should probably also update the description before the note, so
> add 'hit or miss' to the first sentence:
> 
> "EventCode": "0x0396",
> "EventName": "L2D_CACHE_REFILL_L3D_MISS",
> "BriefDescription": "This event counts operations that cause a hit or miss of the L3
> cache. Note that this incorrectly counts both hits _and_ misses."

We will also discuss with the hardware team on this matter.

Best Regards,
Yoshihiro Furudera