linux-kernel - Re: [PATCH] perf vendor events: Update datasource event name to fix duplicate events

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Date:   Tue, 5 Dec 2023 12:46:17 +0530
From:   Athira Rajeev <atrajeev@...ux.vnet.ibm.com>
To:     Ian Rogers <irogers@...gle.com>,
        Arnaldo Carvalho de Melo <acme@...nel.org>,
        Namhyung Kim <namhyung@...nel.org>
Cc:     Kajol Jain <kjain@...ux.ibm.com>,
        Adrian Hunter <adrian.hunter@...el.com>,
        linux-perf-users <linux-perf-users@...r.kernel.org>,
        Madhavan Srinivasan <maddy@...ux.ibm.com>,
        James Clark <james.clark@....com>,
        Jiri Olsa <jolsa@...nel.org>,
        Disha Goel <disgoel@...ux.vnet.ibm.com>,
        linuxppc-dev <linuxppc-dev@...ts.ozlabs.org>,
        LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] perf vendor events: Update datasource event name to fix
 duplicate events



> On 05-Dec-2023, at 2:43 AM, Ian Rogers <irogers@...gle.com> wrote:
> 
> On Mon, Dec 4, 2023 at 12:22 PM Arnaldo Carvalho de Melo
> <acme@...nel.org> wrote:
>> 
>> Em Mon, Dec 04, 2023 at 05:20:46PM -0300, Arnaldo Carvalho de Melo escreveu:
>>> Em Mon, Dec 04, 2023 at 12:12:54PM -0800, Ian Rogers escreveu:
>>>> On Thu, Nov 23, 2023 at 8:01 AM Athira Rajeev
>>>> <atrajeev@...ux.vnet.ibm.com> wrote:
>>>>> 
>>>>> Running "perf list" on powerpc fails with segfault
>>>>> as below:
>>>>> 
>>>>>   ./perf list
>>>>>   Segmentation fault (core dumped)
>>>>> 
>>>>> This happens because of duplicate events in the json list.
>>>>> The powerpc Json event list contains some event with same
>>>>> event name, but different event code. They are:
>>>>> - PM_INST_FROM_L3MISS (Present in datasource and frontend)
>>>>> - PM_MRK_DATA_FROM_L2MISS (Present in datasource and marked)
>>>>> - PM_MRK_INST_FROM_L3MISS (Present in datasource and marked)
>>>>> - PM_MRK_DATA_FROM_L3MISS (Present in datasource and marked)
>>>>> 
>>>>> pmu_events_table__num_events uses the value from
>>>>> table_pmu->num_entries which includes duplicate events as
>>>>> well. This causes issue during "perf list" and results in
>>>>> segmentation fault.
>>>>> 
>>>>> Since both event codes are valid, append _DSRC to the Data
>>>>> Source events (datasource.json), so that they would have a
>>>>> unique name. Also add PM_DATA_FROM_L2MISS_DSRC and
>>>>> PM_DATA_FROM_L3MISS_DSRC events. With the fix, perf list
>>>>> works as expected.
>>>>> 
>>>>> Fixes: fc1435807533 ("perf vendor events power10: Update JSON/events")
>>>>> Signed-off-by: Athira Rajeev <atrajeev@...ux.vnet.ibm.com>
>>>> 
>>>> Given duplicate events creates broken pmu-events.c we should capture
>>>> that as an exception in jevents.py. That way a JEVENTS_ARCH=all build
>>>> will fail if any vendor/architecture would break in this way. We
>>>> should also add JEVENTS_ARCH=all to tools/perf/tests/make. Athira, do
>>>> you want to look at doing this?
>>> 
>>> Should I go ahead and remove this patch till this is sorted out?
>> 
>> I'll keep it, its already in tmp.perf-tools-next, we can go from there
>> and improve this with follow up patches,

Thanks Arnaldo for pulling the fix patch.

> 
> Agreed. I could look to do the follow up but likely won't have a
> chance for a while. If others could help out it would be great. I'd
> like to have the jevents and json be robust enough that we don't trip
> over problems like this and the somewhat similar AmpereOne issue.

Yes Ian.

I will look at adding this with follow up patches and including this as part of tools/perf/tests/make

Thanks
Athira
> 
> Thanks,
> Ian
> 
>> - Arnaldo