From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755869AbZCNQpg (ORCPT ); Sat, 14 Mar 2009 12:45:36 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1751250AbZCNQp0 (ORCPT ); Sat, 14 Mar 2009 12:45:26 -0400 Received: from mx3.mail.elte.hu ([157.181.1.138]:35224 "EHLO mx3.mail.elte.hu" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751108AbZCNQp0 (ORCPT ); Sat, 14 Mar 2009 12:45:26 -0400 Date: Sat, 14 Mar 2009 17:43:58 +0100 From: Ingo Molnar To: Mathieu Desnoyers Cc: Linus Torvalds , linux-kernel@vger.kernel.org, Andrew Morton , Steven Rostedt , ltt-dev@lists.casi.polymtl.ca, Peter Zijlstra , Frederic Weisbecker , Arjan van de Ven , Pekka Paalanen , Arnaldo Carvalho de Melo , "H. Peter Anvin" , Martin Bligh , "Frank Ch. Eigler" , Tom Zanussi , Masami Hiramatsu , KOSAKI Motohiro , Jason Baron , Christoph Hellwig , Jiaying Zhang , Eduard - Gabriel Munteanu , mrubin@google.com, md@google.com Subject: Re: [RFC patch 00/41] LTTng 0.105 core for Linux 2.6.27-rc9 Message-ID: <20090314164358.GB31930@elte.hu> References: <20090305224728.947235917@polymtl.ca> <20090306101142.GA26659@elte.hu> <20090306190224.GF14236@Krystal> <20090311183231.GA24106@elte.hu> <20090313161838.GA2925@Krystal> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20090313161838.GA2925@Krystal> User-Agent: Mutt/1.5.18 (2008-05-17) X-ELTE-VirusStatus: clean 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=3.2.3 -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 * Mathieu Desnoyers wrote: > * Ingo Molnar (mingo@elte.hu) wrote: > > > > * Mathieu Desnoyers wrote: > > > > > > Let me give you a few examples of existing areas of overlap: > > > > > > > > > The corresponding git tree contains also the trace clock > > > > > patches and the lttng instrumentation. The trace clock is > > > > > required to use the tracer, but it can be used without the > > > > > instrumentation : there is already a kprobes and userspace > > > > > event support included in this patchset. > > > > > > > > The latest tracing tree includes > > > > kernel/tracing/trace_clock.c which offers three trace clock > > > > variants, with different performance/precision tradeoffs: > > > > > > > > trace_clock_local() [ for pure CPU-local tracers with no idle > > > > events. This is the fastest but least > > > > coherent tracing clock. ] > > > > > > > > trace_clock() [ intermediate, scalable clock with > > > > usable but imprecise global coherency. ] > > > > > > > > trace_clock_global() [ globally serialized, coherent clock. > > > > It is the slowest but most accurate variant. ] > > > > > > > > Tracing plugins can pick their choice. (This is relatively new > > > > code but you get the idea.) > > > > > > > > > > Hehe this reminds me of the trace clock thread I started a few > > > months ago on LKML. So you guys took over that work ? Nice :) > > > Is it based on the trace-clock patches I proposed back then ? > > > Ah, no. Well I guess we'll have to discuss this too. I agree > > > on the trace_clock_local/trace_clock/trace_clock_global > > > interface, it looks nice. The underlying implementation will > > > have to be discussed though. > > > > Beware: i found the assembly trace_clock() stuff you did back > > then rather ugly ;-) I dont think there's any easy solutions > > here, so i went for this palette of clocks. > > > > Hi Ingo, > > I agree for the palette of clocks to fit all needs. I wonder > what exactly you found ugly in the approach I took with my > trace_clock() implementation ? Maybe you could refresh my > memory, I do not recall writing any part of it in assembly.. ? > But this is a whole different topic. We can discuss this > later. hm, it was months ago. Ok, it must have been this one: http://lkml.org/lkml/2008/11/7/21 http://lkml.org/lkml/2008/11/7/23 indeed no assembly but almost ;-) What i found rather ugly were the cnt32_to_63() complications. Ingo