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Date: Mon, 26 Oct 2009 21:21:13 +0100 From: Ingo Molnar <mingo@...e.hu> To: Arjan van de Ven <arjan@...radead.org> Cc: Pierre-Marc Fournier <pierre-marc.fournier@...ymtl.ca>, GeunSik Lim <leemgs1@...il.com>, Zhaolei <zhaolei@...fujitsu.com>, Wu Fengguang <fengguang.wu@...el.com>, Jesper Juhl <jj@...osbits.net>, Mathieu Desnoyers <mathieu.desnoyers@...ymtl.ca>, Adrian Bunk <bunk@...sta.de>, Harvey Harrison <harvey.harrison@...il.com>, "Robert P. J. Day" <rpjday@...dspring.com>, Jaswinder Singh Rajput <jaswinderrajput@...il.com>, Frederic Weisbecker <fweisbec@...il.com>, Steven Rostedt <rostedt@...dmis.org>, Lai Jiangshan <laijs@...fujitsu.com>, KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>, linux-kernel@...r.kernel.org, Dominique Toupin <dominique.toupin@...csson.com>, Michel Dagenais <michel.dagenais@...ymtl.ca> Subject: Re: Relicensing tracepoints and markers to Dual LGPL v2.1/GPL v2,headers to Dual BSD/GPL * Arjan van de Ven <arjan@...radead.org> wrote: > On Mon, 26 Oct 2009 09:17:49 -0400 > Pierre-Marc Fournier <pierre-marc.fournier@...ymtl.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 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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