From: Ingo Molnar <mingo@elte.hu>
To: Arjan van de Ven <arjan@infradead.org>
Cc: Pierre-Marc Fournier <pierre-marc.fournier@polymtl.ca>,
GeunSik Lim <leemgs1@gmail.com>, Zhaolei <zhaolei@cn.fujitsu.com>,
Wu Fengguang <fengguang.wu@intel.com>,
Jesper Juhl <jj@chaosbits.net>,
Mathieu Desnoyers <mathieu.desnoyers@polymtl.ca>,
Adrian Bunk <bunk@stusta.de>,
Harvey Harrison <harvey.harrison@gmail.com>,
"Robert P. J. Day" <rpjday@mindspring.com>,
Jaswinder Singh Rajput <jaswinderrajput@gmail.com>,
Frederic Weisbecker <fweisbec@gmail.com>,
Steven Rostedt <rostedt@goodmis.org>,
Lai Jiangshan <laijs@cn.fujitsu.com>,
KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>,
linux-kernel@vger.kernel.org,
Dominique Toupin <dominique.toupin@ericsson.com>,
Michel Dagenais <michel.dagenais@polymtl.ca>
Subject: Re: Relicensing tracepoints and markers to Dual LGPL v2.1/GPL v2,headers to Dual BSD/GPL
Date: Mon, 26 Oct 2009 21:21:13 +0100 [thread overview]
Message-ID: <20091026202113.GF24682@elte.hu> (raw)
In-Reply-To: <20091026071832.36405c9a@infradead.org>
* Arjan van de Ven <arjan@infradead.org> wrote:
> On Mon, 26 Oct 2009 09:17:49 -0400
> Pierre-Marc Fournier <pierre-marc.fournier@polymtl.ca> 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.
That too - plus 'being in the kernel repo' does not mean it has to run
in kernel mode. It could be a vdso feature or a library in tools/. I'm
quite sure it's a mistake to ad-hoc export the current tracepoint.c code
to user-space without having it all under the same maintenance envelope.
Ingo
next prev parent reply other threads:[~2009-10-26 20:21 UTC|newest]
Thread overview: 22+ messages / expand[flat|nested] mbox.gz Atom feed top
2009-10-23 16:02 Relicensing tracepoints and markers to Dual LGPL v2.1/GPL v2, headers to Dual BSD/GPL Mathieu Desnoyers
2009-10-23 16:06 ` Mathieu Desnoyers
2009-10-24 21:03 ` Jesper Juhl
2009-10-24 21:22 ` Mathieu Desnoyers
2009-10-26 1:53 ` Wu Fengguang
2009-10-26 2:08 ` Relicensing tracepoints and markers to Dual LGPL v2.1/GPL v2,headers " Zhaolei
2009-10-26 5:03 ` GeunSik Lim
2009-10-26 7:30 ` Ingo Molnar
2009-10-26 8:10 ` GeunSik Lim
2009-10-26 10:17 ` Alan Cox
2009-10-26 11:31 ` Ingo Molnar
2009-10-26 13:45 ` Steven Rostedt
2009-10-26 13:40 ` Steven Rostedt
2009-10-26 13:17 ` Pierre-Marc Fournier
2009-10-26 13:29 ` Steven Rostedt
2009-10-26 16:11 ` Mathieu Desnoyers
2009-10-26 14:18 ` Arjan van de Ven
2009-10-26 16:05 ` Mathieu Desnoyers
2009-10-26 20:21 ` Ingo Molnar [this message]
2009-10-28 14:11 ` Mathieu Desnoyers
2009-10-23 16:31 ` Relicensing tracepoints and markers to Dual LGPL v2.1/GPL v2, headers " Ingo Molnar
2009-10-23 17:02 ` Mathieu Desnoyers
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