Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1750795AbWIVHPa (ORCPT ); Fri, 22 Sep 2006 03:15:30 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1750822AbWIVHPa (ORCPT ); Fri, 22 Sep 2006 03:15:30 -0400 Received: from mx2.mail.elte.hu ([157.181.151.9]:17895 "EHLO mx2.mail.elte.hu") by vger.kernel.org with ESMTP id S1750795AbWIVHP3 (ORCPT ); Fri, 22 Sep 2006 03:15:29 -0400 Date: Fri, 22 Sep 2006 09:07:14 +0200 From: Ingo Molnar To: Mathieu Desnoyers Cc: Martin Bligh , "Frank Ch. Eigler" , Masami Hiramatsu , prasanna@in.ibm.com, Andrew Morton , Paul Mundt , linux-kernel , Jes Sorensen , Tom Zanussi , Richard J Moore , Michel Dagenais , Christoph Hellwig , Greg Kroah-Hartman , Thomas Gleixner , William Cohen , ltt-dev@shafik.org, systemtap@sources.redhat.com, Alan Cox Subject: Re: [PATCH] Linux Kernel Markers 0.5 for Linux 2.6.17 (with probe management) Message-ID: <20060922070714.GB4167@elte.hu> References: <20060921160009.GA30115@Krystal> <20060921160656.GA24774@elte.hu> <20060921214248.GA10097@Krystal> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20060921214248.GA10097@Krystal> User-Agent: Mutt/1.4.2.1i X-ELTE-SpamScore: -2.9 X-ELTE-SpamLevel: X-ELTE-SpamCheck: no X-ELTE-SpamVersion: ELTE 2.0 X-ELTE-SpamCheck-Details: score=-2.9 required=5.9 tests=ALL_TRUSTED,AWL,BAYES_50 autolearn=no SpamAssassin version=3.0.3 -3.3 ALL_TRUSTED Did not pass through any untrusted hosts 0.5 BAYES_50 BODY: Bayesian spam probability is 40 to 60% [score: 0.4986] -0.1 AWL AWL: From: address is in the auto white-list X-ELTE-VirusStatus: clean Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2412 Lines: 59 * Mathieu Desnoyers wrote: > I clearly expressed my position in the previous emails, so did you. > You argued about a use of tracing that is not relevant to my vision of > reality, which is : > > - Embedded systems developers won't want a breakpoint-based probe are you arguing that i'm trying to force breakpoint-based probing on you? I dont. In fact i explicitly mentioned that i'd accept and support a 5-byte NOP in the body of the marker, in the following mails: "just go for [...] the 5-NOP variant" http://marc.theaimsgroup.com/?l=linux-kernel&m=115859771924187&w=2 (my reply to your second proposal) "or at most one NOP" http://marc.theaimsgroup.com/?l=linux-kernel&m=115865412332230&w=2 (my reply to your third proposal) "at most a NOP inserted" http://marc.theaimsgroup.com/?l=linux-kernel&m=115886524224874&w=2 (my reply to your fifth proposal) That enables the probe to be turned into a function call - not an INT3 breakpoint. Does it take some effort to implement that on your part? Yes, of course, but getting code upstream is never easy, /especially/ in cases where most of the users wont use a particular feature. > - High performance computing users won't want a breakpoint-based probe I am not forcing breakpoint-based probing, at all. I dont want _static, build-time function call based_ probing, and there is a big difference. And one reason why i want to avoid "static, build-time function call based probing" is because high-performance computing users dont want any overhead at all in the kernel fastpath. > - djprobe is far away from being in an acceptable state on > architectures with very inconvenient erratas (x86). djprobes over a NOP marker are perfectly usable and safe: just add a simple constraint to them to only allow a djprobes insertion if it replaces a 5-byte NOP. > - kprobe and djprobe cannot access local variables in every cases it is possible with the marker mechanism i outlined before: http://marc.theaimsgroup.com/?l=linux-kernel&m=115886524224874&w=2 have i missed to address any concern of yours? 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/