linux-kernel - Re: [PATCH v1 3/9] perf auxtrace: Refactor auxtrace__evsel_is

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Message-ID: <8258c91a-ab6c-42f0-a77c-dea52201deec@linaro.org>
Date: Fri, 9 Aug 2024 11:08:45 +0100
From: James Clark <james.clark@...aro.org>
To: Adrian Hunter <adrian.hunter@...el.com>, Leo Yan <leo.yan@....com>
Cc: Arnaldo Carvalho de Melo <acme@...nel.org>,
 Namhyung Kim <namhyung@...nel.org>, Ian Rogers <irogers@...gle.com>,
 Suzuki K Poulose <suzuki.poulose@....com>, Mike Leach
 <mike.leach@...aro.org>, coresight@...ts.linaro.org,
 linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
 "Liang, Kan" <kan.liang@...ux.intel.com>
Subject: Re: [PATCH v1 3/9] perf auxtrace: Refactor
 auxtrace__evsel_is_auxtrace()



On 08/08/2024 1:58 pm, Adrian Hunter wrote:
> On 6/08/24 23:41, Leo Yan wrote:
>> The auxtrace__evsel_is_auxtrace() function invokes the callback
>> .evsel_is_auxtrace() to check if an event is an AUX trace. In the
>> low-level code, every AUX trace module provides its callback to
>> compare the PMU type.
>>
>> This commit refactors auxtrace__evsel_is_auxtrace() by simply
>> calling evsel__is_aux_event() rather than using the callback function.
>> As a result, the callback .evsel_is_auxtrace() is no longer needed, so
>> the definition and implementations are removed.
> 
> evsel__is_aux_event() assumes it is on the target machine e.g.
> being called from perf record.  It indirectly reads from sysfs
> to find PMUs, which will not necessarily be the same a different
> machine.
> 
> For example, what happens if a perf data file from one arch is
> being processed on a machine from another arch.
> 

I think this does go a bit wrong. If I open an SPE file on x86 it finds 
the intel_pt PMU which both have the same type number. But because 
that's also an auxtrace one it appears to work.