linux-kernel - Re: [PATCH] perf sched replay: fix event lookup

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Message-ID: <8739616pc9.fsf@sejong.aot.lge.com>
Date:	Tue, 12 Jun 2012 15:01:26 +0900
From:	Namhyung Kim <namhyung@...nel.org>
To:	Arnaldo Carvalho de Melo <acme@...stprotocols.net>
Cc:	Dmitry Antipov <dmitry.antipov@...aro.org>,
	Ingo Molnar <mingo@...hat.com>,
	Paul Mackerras <paulus@...ba.org>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	linux-kernel@...r.kernel.org, linaro-dev@...ts.linaro.org,
	patches@...aro.org
Subject: Re: [PATCH] perf sched replay: fix event lookup

Hi,

On Mon, 11 Jun 2012 11:08:52 -0300, Arnaldo Carvalho de Melo wrote:
> Em Mon, Jun 11, 2012 at 02:46:02PM +0900, Namhyung Kim escreveu:
>> On Sat,  9 Jun 2012 13:05:58 +0400, Dmitry Antipov wrote:
>> > Use new function trace_find_event_by_name to lookup events before
>> > looking through /sys files. This helps 'perf sched replay' to map
>> > event names to IDs correctly when processing perf.data recorded
>> > on another machine.
>> 
>> Basically the same approach with the previous reply, please put this
>> into trace_event__id(). And minor nits below..
>
> Well, trace_event__id() is private to evlist and evlist so far is a
> local thing, i.e. it doesn't know anything about perf.data files.
>

Really? I see that perf_session__open make up an evlist for the session
and a tracepoint event in the evlist should look up the perf.data
first. As this patch addressed, perf sched replay dealt with the
session->evlist already. Am I missing something?


> So I think we should have a per perf.data (perf_session) method that
> knows that it shouldn't look _at all_ to /sys, but just at what came in
> the perf.data file.
>

Fair enough. The method should be a simple wrapper to libtraceevent APIs
like this patch.


> As well when we want something that is on the running machine, even if
> we're dealing somehow with a perf.data file, we shouldn't use what is in
> it.
>

That's the current behavior of the trace_event__id(). Do you want to
make it public?

Thanks,
Namhyung
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