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Date: Thu, 27 Aug 2009 15:35:02 +0200
From: Frederic Weisbecker <fweisbec@gmail.com>
To: Ingo Molnar <mingo@elte.hu>
Cc: Peter Zijlstra <peterz@infradead.org>,
       Steven Rostedt <rostedt@goodmis.org>,
       Arjan van de Ven <arjan@infradead.org>,
       Paul Mackerras <paulus@samba.org>, Thomas Gleixner <tglx@linutronix.de>,
       Andrew Morton <akpm@linux-foundation.org>,
       Linus Torvalds <torvalds@linux-foundation.org>,
       Christoph Hellwig <hch@infradead.org>,
       LKML <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH] perf: remove PERF_SAMPLE_RAW
Message-ID: <20090827133455.GB6058@nowhere>
References: <1251361073.18584.46.camel@twins> <20090827084321.GD2131@elte.hu>
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On Thu, Aug 27, 2009 at 10:43:21AM +0200, Ingo Molnar wrote:
> * Peter Zijlstra <peterz@infradead.org> wrote:
> 
> > Apparently people think trace-events became an ABI the moment perf 
> > exported them, regardless what the text surrounding 
> > PERF_SAMPLE_RAW said about the opaqueness of the data provided.
> 
> Well it's still opaque and the descriptor of what it means is in 
> debugfs so it's not an ABI as the comment says.
> 
> > I'm not willing to make anything trace related into an ABI, hence 
> > remove this.
> 
> This removes quite a bit of nice functionality we already have, so i 
> think it's (way) too heavy handed.
> 
> I think what we want is the golden middle: a per tracepoint 
> property. I.e. we would provide:
> 
>     TRACE_EVENT_STABLE()
> 
> or TRACE_EVENT_CORE() or TRACE_EVENT_ABI() - which carries a 'will 
> maintain this as an ABI' promise from the maintainer who adds it.


Why? The format files stand to avoid that.

I don't understand this debate.


> Also, tracepoints are a unidirectional channel of information - in 
> practice those are way easier to handle as an ABI than other ABIs 
> such as behavior, semantics, etc. So i'd expect there to be a 
> healthy set of 'stable' tracepoints.
> 
> 	Ingo