linux-kernel - Re: [PATCH 0/11] LTTng-core (basic tracing infrastructure) 0.5.108

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Date:	Sat, 16 Sep 2006 10:21:54 +0200
From:	Ingo Molnar <mingo@...e.hu>
To:	Roman Zippel <zippel@...ux-m68k.org>
Cc:	Thomas Gleixner <tglx@...utronix.de>, karim@...rsys.com,
	Andrew Morton <akpm@...l.org>,
	Paul Mundt <lethal@...ux-sh.org>, Jes Sorensen <jes@....com>,
	Mathieu Desnoyers <mathieu.desnoyers@...ymtl.ca>,
	linux-kernel@...r.kernel.org,
	Christoph Hellwig <hch@...radead.org>,
	Ingo Molnar <mingo@...hat.com>,
	Greg Kroah-Hartman <gregkh@...e.de>,
	Tom Zanussi <zanussi@...ibm.com>, ltt-dev@...fik.org,
	Michel Dagenais <michel.dagenais@...ymtl.ca>
Subject: Re: [PATCH 0/11] LTTng-core (basic tracing infrastructure) 0.5.108

* Roman Zippel <zippel@...ux-m68k.org> wrote:

> > > > > This is simply not true, at the source level you can remove a 
> > > > > static tracepoint as easily as a dynamic tracepoint, the 
> > > > > effect of the missing trace information is the same either way.
> > > >
> > > > this is not true. I gave you one example already a few mails ago
> > > > [...]
> > >
> > > Function attributes also doesn't provide information local to the 
> > > function.
> > 
> > of course, but where does the above tracepoint i quoted use 
> > information local to the function? A fair number of markups use 
> > global functions because, surprise, alot of interesting activity 
> > happens along global functions. So a healthy reduction in markups 
> > can be achieved.
> 
> But not completely, which is the whole point.

the point was what you said above, which i claimed and still claim to be 
false: "at the source level you can remove a static tracepoint as easily 
as a dynamic tracepoint, the effect of the missing trace information is 
the same either way."

Your point is still incorrect. I gave you an example of how half of the 
tracepoints could be removed under a dynamic scheme - while they couldnt 
be removed under a static scheme. Hence that directly contradicts your 
contention that "you can remove a static tracepoint as easily as a 
dynamic tracepoint". Nothing more, nothing less. I just pointed out the 
point in your thinking that i believe to be incorrect.

Reality is that you can remove a dynamic tracepoint much easier, due to 
the fundamental flexibility of dynamic tracers. While with static 
tracers, every tracepoint has to be _somewhere_ in the source code, 
otherwise people like you will complain just like you did in this mail: 
"you make life more difficult for static tracers for no reason".

You can concede my point or you can dispute that argument - but what you 
did above was neither: you snipped all the quotations and you claimed a 
totally new point. (which new point i never argued with: _of course_ i 
never claimed that __trace function attributes can remove _all_ markups. 
They can "only" remove half of them.)

	Ingo
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