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

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Date:	Sun, 09 Aug 2009 16:10:12 -0700
From:	Arjan van de Ven <arjan@...ux.intel.com>
To:	Frederic Weisbecker <fweisbec@...il.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

Frederic Weisbecker wrote:
> 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.
> 

ok I'll unstatic it, move it to a different file and ..

eh how about not?

this helper looks up an on disk id/name pair, and is private to it's existing file.
Fine.

The other one is based on the perf data, and all that is in header.c instead....


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