linux-kernel - Re: s390 perf events JSONs query

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Date:   Fri, 20 Apr 2018 15:25:05 +0200
From:   Thomas-Mich Richter <tmricht@...ux.ibm.com>
To:     John Garry <john.garry@...wei.com>, brueckner@...ux.vnet.ibm.com,
        tmricht@...ux.vnet.ibm.com
Cc:     Peter Zijlstra <peterz@...radead.org>,
        Ingo Molnar <mingo@...hat.com>,
        Arnaldo Carvalho de Melo <acme@...nel.org>,
        Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
        Jiri Olsa <jolsa@...hat.com>,
        Namhyung Kim <namhyung@...nel.org>,
        Linuxarm <linuxarm@...wei.com>, linux-kernel@...r.kernel.org,
        Will Deacon <will.deacon@....com>
Subject: Re: s390 perf events JSONs query

On 04/20/2018 12:51 PM, John Garry wrote:
> Hi Hendrik, Thomas,
> 
> I noticed that in 4.17-rc1 support was included for s390 perf pmu-events. I also notice that the JSONs contain many common (identical actually) events between different chips for this arch.
> 
> Support was added for factoring out common arch events in https://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git/commit/tools/perf/pmu-events?h=next-20180420&id=e9d32c1bf0cd7a98358ec4aa1625bf2b3459b9ac
> 
> ARM64 chips use this feature. I am not familiar with the s390 arch, but do you think you could also use this feature?
> 
> Thanks,
> John
> 

I have just played with this feature. I was caught off by this error message:

[root@...lp76 pmu-events]# ./jevents s390 arch /tmp/xxx 100000
d 0    4096 s390                 arch/s390
d 1    4096 cf_z14               arch/s390/cf_z14
f 2    1338 basic.json           arch/s390/cf_z14/basic.json
....
jevents: Ignoring file arch/s390/archevent.json  <---- confusing error message

jevents: Processing mapfile arch/s390/mapfile.csv
[root@...lp76 pmu-events]# 

I started debugging, until I realized this file is still processed.....
(Just a side remark).

Anyway the features is nice, but it does not save anything in the resulting
pmu-events.c file, correct? The events defined in the common archevent.json
files are just copied into the structures of a specific machine.

The feature saves time and space when you create the machine specific json
files because it allows you to refer to a common event by name. Cool!

On s390 we do not create the json files manually, but have some scripts to
create them based on s390 type/model hardware specific input files.

@Hendirk,
we could rework our internal tool chain to emit the new "ArchStdEvent"
keyword for common events, but in the end we do not save anything in the
resulting pmu-events.c file. And it requires considerable rework to 
support it.
Given that, I would put it very low priority on your todo list, comments?

-- 
Thomas Richter, Dept 3303, IBM LTC Boeblingen Germany
--
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