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

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Message-Id: <20081125211750.26F3.KOSAKI.MOTOHIRO@jp.fujitsu.com>
Date:	Tue, 25 Nov 2008 21:23:57 +0900 (JST)
From:	KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>
To:	Ingo Molnar <mingo@...e.hu>, fche@...hat.com (Frank Ch. Eigler)
Cc:	kosaki.motohiro@...fujitsu.com,
	Mathieu Desnoyers <mathieu.desnoyers@...ymtl.ca>,
	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())

Hi

Sorry for very late responce.
However, if you do marker removing disucussion, I hope CC to Frank Eigler.
because SystemTap also use marker and tracepoint.
and this patch also improvement SystemTap marker support, I think.

IIRC, Currently, Systemtap also have marker/tracepoint on/off
syncronization problem.


> > 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() ?

Frank, Could you please read this thread and give us your comment?



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