Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755017AbZJZUVi (ORCPT ); Mon, 26 Oct 2009 16:21:38 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1754216AbZJZUVi (ORCPT ); Mon, 26 Oct 2009 16:21:38 -0400 Received: from mx2.mail.elte.hu ([157.181.151.9]:39918 "EHLO mx2.mail.elte.hu" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752398AbZJZUVh (ORCPT ); Mon, 26 Oct 2009 16:21:37 -0400 Date: Mon, 26 Oct 2009 21:21:13 +0100 From: Ingo Molnar To: Arjan van de Ven Cc: Pierre-Marc Fournier , 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 , linux-kernel@vger.kernel.org, Dominique Toupin , Michel Dagenais Subject: Re: Relicensing tracepoints and markers to Dual LGPL v2.1/GPL v2,headers to Dual BSD/GPL Message-ID: <20091026202113.GF24682@elte.hu> References: <20091023160257.GA30447@Krystal> <20091023160632.GA2198@Krystal> <20091026015357.GA6033@localhost> <023001ca55e1$436e38e0$808410ac@zhaoleiwin> <49b7c2350910252203o69811000w4551c01e6e2a10c7@mail.gmail.com> <20091026073048.GC8162@elte.hu> <4AE5A17D.5020202@polymtl.ca> <20091026071832.36405c9a@infradead.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20091026071832.36405c9a@infradead.org> User-Agent: Mutt/1.5.19 (2009-01-05) X-ELTE-SpamScore: -1.5 X-ELTE-SpamLevel: X-ELTE-SpamCheck: no X-ELTE-SpamVersion: ELTE 2.0 X-ELTE-SpamCheck-Details: score=-1.5 required=5.9 tests=BAYES_00 autolearn=no SpamAssassin version=3.2.5 -1.5 BAYES_00 BODY: Bayesian spam probability is 0 to 1% [score: 0.0000] Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1358 Lines: 33 * Arjan van de Ven wrote: > 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. 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@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/