linux-kernel - Re: [patch 06/16] Markers auto enable tracepoints (new API : trace_mark

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Message-ID: <20081116075928.GB530@elte.hu>
Date:	Sun, 16 Nov 2008 08:59:28 +0100
From:	Ingo Molnar <mingo@...e.hu>
To:	Mathieu Desnoyers <mathieu.desnoyers@...ymtl.ca>
Cc:	linux-kernel@...r.kernel.org, akpm@...ux-foundation.org,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Lai Jiangshan <laijs@...fujitsu.com>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	Thomas Gleixner <tglx@...utronix.de>
Subject: Re: [patch 06/16] Markers auto enable tracepoints (new API :
	trace_mark_tp())

* Mathieu Desnoyers <mathieu.desnoyers@...ymtl.ca> wrote:

> Add a new API trace_mark_tp(), which declares a marker within a 
> tracepoint probe. When the marker is activated, the tracepoint is 
> automatically enabled.
> 
> No branch test is used at the marker site, because it would be a 
> duplicate of the branch already present in the tracepoint.
> 
> Impact: new API.

i dont know.

I was actually hoping for markers (the in-kernel API) to go away 
completely - and be replaced with tracepoints.

Markers are the wrong design on several levels. They couple the kernel 
dynamically with unknown (to the kernel) entities - and that is 
causing complexity all around the place, clearly expressed in these 
patches of yours.

Tracepoints are much more specific - typed and enumerated function 
call callback points in essence - with some politeness that allows 
external instrumentation entities to attach to those callbacks.

Is there any usecase of markers that should not be converted to either 
tracepoints or to ftrace_printk() ?

	Ingo
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