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Date:	Mon, 26 Oct 2009 07:18:32 -0700
From:	Arjan van de Ven <>
To:	Pierre-Marc Fournier <>
Cc:	Ingo Molnar <>, GeunSik Lim <>,
	Zhaolei <>,
	Wu Fengguang <>,
	Jesper Juhl <>,
	Mathieu Desnoyers <>,
	Adrian Bunk <>,
	Harvey Harrison <>,
	"Robert P. J. Day" <>,
	Jaswinder Singh Rajput <>,
	Frederic Weisbecker <>,
	Steven Rostedt <>,
	Lai Jiangshan <>,
	KOSAKI Motohiro <>,,
	Dominique Toupin <>,
	Michel Dagenais <>
Subject: Re: Relicensing tracepoints and markers to Dual LGPL v2.1/GPL
 v2,headers to Dual BSD/GPL

On Mon, 26 Oct 2009 09:17:49 -0400
Pierre-Marc Fournier <> wrote:

> Ingo Molnar wrote:
> > 
> > But i also disagree with it on a technical level: code duplication
> > is _bad_. Why does the code have to be duplicated in user-space
> > like that? I'd like Linux tracing code to be in the kernel repo.
> > Why isnt this done properly, as part of the kernel project - to
> > make sure it all stays in sync?
> > 
> If you mean that this code should solely be used inside the kernel,
> then what you propose technically does not work. There is a very high
> cost to accessing kernel code from userspace. 

yeah 100 cycles is insanely high, that's at least the equivalent of...
say one cache miss.

Arjan van de Ven 	Intel Open Source Technology Centre
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