From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1763468AbYDONSe (ORCPT ); Tue, 15 Apr 2008 09:18:34 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1753637AbYDONS0 (ORCPT ); Tue, 15 Apr 2008 09:18:26 -0400 Received: from mx3.mail.elte.hu ([157.181.1.138]:52528 "EHLO mx3.mail.elte.hu" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753210AbYDONS0 (ORCPT ); Tue, 15 Apr 2008 09:18:26 -0400 Date: Tue, 15 Apr 2008 15:17:44 +0200 From: Ingo Molnar To: Peter Zijlstra Cc: Mathieu Desnoyers , prasad@linux.vnet.ibm.com, linux-kernel@vger.kernel.org, tglx@linutronix.de, Christoph Hellwig , "Frank Ch. Eigler" Subject: Re: [RFC PATCH 1/2] Marker probes in futex.c Message-ID: <20080415131744.GA5248@elte.hu> References: <20080415115058.GA6788@in.ibm.com> <20080415115314.GA6975@in.ibm.com> <1208260942.6395.6.camel@twins> <20080415123233.GA19797@Krystal> <1208264190.6395.21.camel@twins> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1208264190.6395.21.camel@twins> User-Agent: Mutt/1.5.17 (2007-11-01) 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 * Peter Zijlstra wrote: > > Because we extract the field names and types, we can create tracer > > plugins that would hook on field names rather than expect a specific > > number of fields and fixed field types. It makes it possible to > > tolerate missing fields pretty easily. But yes, tracer tools might > > have to be adapted to internal kernel changes, since they must > > follow kernel structure changes. However, staying as close as > > possible to a canonical representation of event fields, staying far > > from the specific implemetation, would help to lessen the > > inter-dependency. On the other hand, it would probably hurt trace > > compactness and efficiency. > > See, these tracer tools are my nightmare as member of an enterprise > linux team. They'll make an already hard job even harder, no thanks! i'm clearly NAK-ing all futex trace hooks until the true impact of the whole marker facility is better understood. I've tried them for the scheduler and they were a clear failure: too bloated and too persistent. but more importantly, as things stand today i've yet to see a _any_ bugreport where these 'tracer' tools that are being referred to were actually used in the field to fix something. The latency tracers (and the other tracer variants in -rt) on the other hand have a documented track record of being useful in fixing bugs and instrumenting the kernel. Ingo