linux-kernel - Re: [RFC/PATCHSET 00/19] perf stat: Cleanup counter aggregation (v1)

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Message-ID: <c65f10bd-e486-42d7-b221-dd763623775d@linux.intel.com>
Date:   Tue, 11 Oct 2022 07:57:11 -0400
From:   Andi Kleen <ak@...ux.intel.com>
To:     Namhyung Kim <namhyung@...nel.org>
Cc:     Arnaldo Carvalho de Melo <acme@...nel.org>,
        Jiri Olsa <jolsa@...nel.org>, Ingo Molnar <mingo@...nel.org>,
        Peter Zijlstra <peterz@...radead.org>,
        LKML <linux-kernel@...r.kernel.org>,
        Ian Rogers <irogers@...gle.com>,
        Adrian Hunter <adrian.hunter@...el.com>,
        linux-perf-users@...r.kernel.org,
        Kan Liang <kan.liang@...ux.intel.com>,
        Leo Yan <leo.yan@...aro.org>,
        Athira Rajeev <atrajeev@...ux.vnet.ibm.com>,
        James Clark <james.clark@....com>,
        Xing Zhengjun <zhengjun.xing@...ux.intel.com>
Subject: Re: [RFC/PATCHSET 00/19] perf stat: Cleanup counter aggregation (v1)


>> My main concern would be subtle regressions since there are so many
>> different combinations and way to travel through the code, and a lot of
>> things are not covered by unit tests. When I worked on the code it was
>> difficult to keep it all working. I assume you have some way to
>> enumerate them all and tested that the output is identical?
> Right, that's my concern too.
>
> I have tested many combinations manually and checked if they
> produced similar results.

I had a script to test many combinations, but had to check the output 
manually


> But the problem is that I cannot test
> all hardwares and more importantly it's hard to check
> programmatically if the output is the same or not.

Can use "dummy" or some software event (e.g. a probe on some syscall) to 
get stable numbers. I don't think we need to cover all hardware for the 
output options, the different events should be similar, but need some 
coverage for the different aggregation. Or we could add some more tool 
events just for testing purposes, that would allow covering different 
core scopes etc. and would easily allow generating known counts.

-Andi