Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932324AbWIPIbQ (ORCPT ); Sat, 16 Sep 2006 04:31:16 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S932322AbWIPIbP (ORCPT ); Sat, 16 Sep 2006 04:31:15 -0400 Received: from mx2.mail.elte.hu ([157.181.151.9]:6023 "EHLO mx2.mail.elte.hu") by vger.kernel.org with ESMTP id S932321AbWIPIbN (ORCPT ); Sat, 16 Sep 2006 04:31:13 -0400 Date: Sat, 16 Sep 2006 10:23:10 +0200 From: Ingo Molnar To: Roman Zippel Cc: Thomas Gleixner , karim@opersys.com, Andrew Morton , Paul Mundt , Jes Sorensen , Mathieu Desnoyers , linux-kernel@vger.kernel.org, Christoph Hellwig , Ingo Molnar , Greg Kroah-Hartman , Tom Zanussi , ltt-dev@shafik.org, Michel Dagenais Subject: Re: [PATCH 0/11] LTTng-core (basic tracing infrastructure) 0.5.108 Message-ID: <20060916082310.GE6317@elte.hu> References: <1158348954.5724.481.camel@localhost.localdomain> <450B0585.5070700@opersys.com> <1158351780.5724.507.camel@localhost.localdomain> <20060915204812.GA6909@elte.hu> <20060915215112.GB12789@elte.hu> <20060915231419.GA24731@elte.hu> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: 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: 0.5000] -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: 2929 Lines: 65 * Roman Zippel wrote: > > > > > > - a marker for dynamic tracing has lower performance impact ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ > > > > > > than a static tracepoint, on systems that are not being ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ > > > > > > traced. (but which have the tracing infrastructure enabled ^^^^^^ > > > > > > otherwise) > > > > > > > > > > Anyone using static tracing intents to use, which makes this point > > > > > moot. > > > > > > > > that's not at all true, on multiple grounds: > > > > > > > > Firstly, many people use distro kernels. A Linux distribution > > > > typically wants to offer as few kernel rpms as possible (one per > > > > arch to be precise), but it also wants to offer as many features > > > > as possible. So if there was a static tracer in there, a distro > > > > would enable it - but 99.9% of the users would never use it - still > > > > they would see the overhead. Hence the user would have it enabled, > > > > but does not intend to use it - which contradicts your statement. > > > > > > So if dynamic tracing is available use it, as distributions > > > already do. OTOH the barrier to use static tracing is drastically > > > different whether the user has to deal with external patches or > > > whether it's a simple kernel option. Again, static tracing doesn't > > > exclude the possibility of dynamic tracing, that's something you > > > constantly omit and thus make it sound like both options were > > > mutually exlusive. > > > > how does this reply to my point that: "a marker for dynamic tracing has > > lower performance impact than a static tracepoint, on systems that are > > not being traced", which point you claimed moot? > > Because it's pretty much an implementation issue. [...] No, that's my point, it's not an "implementational issue" of static tracers, the overhead of markups for static tracers is: _inherent to their concept of being compile-time and static_ ok? > [...] The point is about adding markers at all, it's about the choice > being able to use static tracers in the first place. [...] your characterization of "the point" is at odds with the specific point that we are discussing - see the underlined sentence above, right at the top of the quotes: > > > > > > - a marker for dynamic tracing has lower performance impact > > > > > > than a static tracepoint, on systems that are not being > > > > > > traced. (but which have the tracing infrastructure enabled Please either concede the point or dispute it, before shifting to new grounds. Thanks, 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/