From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (qmail 11153 invoked by alias); 10 Jul 2008 18:20:26 -0000 Received: (qmail 11140 invoked by uid 22791); 10 Jul 2008 18:20:25 -0000 X-Spam-Status: No, hits=-2.5 required=5.0 tests=AWL,BAYES_00,SPF_HELO_PASS,SPF_PASS X-Spam-Check-By: sourceware.org Received: from mx1.redhat.com (HELO mx1.redhat.com) (66.187.233.31) by sourceware.org (qpsmtpd/0.31) with ESMTP; Thu, 10 Jul 2008 18:20:05 +0000 Received: from int-mx1.corp.redhat.com (int-mx1.corp.redhat.com [172.16.52.254]) by mx1.redhat.com (8.13.8/8.13.8) with ESMTP id m6AIJbp0018223; Thu, 10 Jul 2008 14:19:37 -0400 Received: from pobox-3.corp.redhat.com (pobox-3.corp.redhat.com [10.11.255.67]) by int-mx1.corp.redhat.com (8.13.1/8.13.1) with ESMTP id m6AIJbVF018878; Thu, 10 Jul 2008 14:19:37 -0400 Received: from touchme.toronto.redhat.com (IDENT:postfix@touchme.yyz.redhat.com [10.15.16.9]) by pobox-3.corp.redhat.com (8.13.1/8.13.1) with ESMTP id m6AIIu53002774; Thu, 10 Jul 2008 14:19:29 -0400 Received: from ton.toronto.redhat.com (ton.yyz.redhat.com [10.15.16.15]) by touchme.toronto.redhat.com (Postfix) with ESMTP id E82228001FF; Thu, 10 Jul 2008 14:18:39 -0400 (EDT) Received: from ton.toronto.redhat.com (localhost.localdomain [127.0.0.1]) by ton.toronto.redhat.com (8.13.1/8.13.1) with ESMTP id m6AIIN95024174; Thu, 10 Jul 2008 14:18:23 -0400 Received: (from fche@localhost) by ton.toronto.redhat.com (8.13.1/8.13.1/Submit) id m6AIIMXU024173; Thu, 10 Jul 2008 14:18:22 -0400 Date: Thu, 10 Jul 2008 18:20:00 -0000 From: "Frank Ch. Eigler" To: Theodore Tso , James Bottomley , linux-kernel , systemtap@sourceware.org Subject: Re: [RFC] simple dprobe like markers for the kernel Message-ID: <20080710181822.GA20174@redhat.com> References: <1215638551.3444.39.camel__22002.9595810503$1215638656$gmane$org@localhost.localdomain> <1215697794.3353.5.camel@localhost.localdomain> <20080710142208.GC1213@redhat.com> <1215700996.3353.30.camel@localhost.localdomain> <20080710153017.GB25939@mit.edu> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20080710153017.GB25939@mit.edu> User-Agent: Mutt/1.4.1i X-Scanned-By: MIMEDefang 2.58 on 172.16.52.254 Mailing-List: contact systemtap-help@sourceware.org; run by ezmlm Precedence: bulk List-Id: List-Subscribe: List-Post: List-Help: , Sender: systemtap-owner@sourceware.org X-SW-Source: 2008-q3/txt/msg00134.txt.bz2 Hi - On Thu, Jul 10, 2008 at 11:30:17AM -0400, Theodore Tso wrote: > [...] When you said a tool could determine if the tracepoint had > gotten optimized away, or the variables were no longer present, I > assume you meant at compile time, right? So with the right tool > built into the kbuild infrastructure, if we could simply print > warnings when tracepoints had gotten optimized away [...] It will be interesting to see how frequently such a warning appears for a good suite of such mini markers, on a diversity of architectures and compilers. Such data can help pronounce judgement on this approach. > P.S. When you said that the current kernel markers are "a bit > heavyweight", how bad are they in practice? Hundreds of cycles? More? Good question. The only performance measurements I have seen posted indicate negligible effects. - FChE