linux-kernel - Re: perf: store and retrieve trace event names in the perf.data file

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Message-ID: <20090809230430.GB6089@nowhere>
Date:	Mon, 10 Aug 2009 01:04:31 +0200
From:	Frederic Weisbecker <fweisbec@...il.com>
To:	Arjan van de Ven <arjan@...ux.intel.com>
Cc:	Ingo Molnar <mingo@...e.hu>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: perf: store and retrieve trace event names in the perf.data file

On Sun, Aug 09, 2009 at 04:01:30PM -0700, Arjan van de Ven wrote:
> Frederic Weisbecker wrote:
>> On Sun, Aug 09, 2009 at 02:49:23PM -0700, Arjan van de Ven wrote:
>>> In order to be able to use trace events, a key aspect is the "type" field;
>>> this is the id of the event that you recorded, as stored in the /sys/kernel/debug/events/*/*/id file.
>>> What is currently missing is a way to map the id number (which is not abi stable)
>>> to the event that was recorded.
>>
>>
>>
>> We already have that.
>> See tools/perf/util/parse-events.c: char *tracepoint_id_to_name(u64 id)
>
>
> sadly... we don't.
>
> You do it *on the same boot and machine* as you created the perf.data file.
> You don't have it when you reboot into a new kernel, or move the perf.data file
> to a new machine........
>
> Which is to be honest a very common usecase.


Ah right... I always forget the offline report case.
But you can at least reuse this existing helper to resolve
the id to name.

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