linux-kernel - Re: Perf record format portability

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Message-ID: <4FB4885F.4000002@linaro.org>
Date:	Thu, 17 May 2012 09:10:55 +0400
From:	Dmitry Antipov <dmitry.antipov@...aro.org>
To:	Steven Rostedt <rostedt@...dmis.org>
CC:	Arnaldo Carvalho de Melo <acme@...stprotocols.net>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	Paul Mackerras <paulus@...ba.org>,
	Ingo Molnar <mingo@...hat.com>,
	Amit Kucheria <amit.kucheria@...aro.org>,
	linaro-dev@...ts.linaro.org, linux-kernel@...r.kernel.org,
	Jiri Olsa <jolsa@...hat.com>
Subject: Re: Perf record format portability

On 05/16/2012 08:58 PM, Steven Rostedt wrote:

> On Wed, 2012-05-16 at 11:59 -0300, Arnaldo Carvalho de Melo wrote:
>
>> Steve,
>>
>> 	Was the kernel trace events infrastructure designed with that in
>> mind? I.e. cross analysis? I must be missing something here, still
>> ENOCOFFEE :-\
>
> Yes, the libparsevents library was design for this from day one. That's
> why trace-cmd data file can be run on an ARM and read on x86, or PPC, or
> whatever. I did all my development testing against 32bit, 64bit and big
> and little endian. This was the case from the beginning.

I didn't face with big/little conversion issues, most probably both x86 and
my ARM board are of the same (little) endian :-).

But the original question was about event IDs. For example,
/sys/kernel/debug/tracing/events/sched/sched_switch/id is 55 on my ARM board
and 279 on my PC host, so 'perf report' displays "unknown:unknown" instead
of expected "sched:sched_switch" when attempting to do some cross-analysis.
I suppose that original event IDs should be preserved, either within perf.data
or by providing the copy of original /sys/kernel/debug/tracing/*, much like
it's done with --kallsyms to resolve kernel symbols.

Dmitry
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