From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (qmail 5811 invoked by alias); 16 Nov 2007 22:35:00 -0000 Received: (qmail 5407 invoked by uid 22791); 16 Nov 2007 22:34:57 -0000 X-Spam-Status: No, hits=-2.4 required=5.0 tests=AWL,BAYES_00,DK_POLICY_SIGNSOME,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; Fri, 16 Nov 2007 22:34:52 +0000 Received: from int-mx1.corp.redhat.com (int-mx1.corp.redhat.com [172.16.52.254]) by mx1.redhat.com (8.13.8/8.13.1) with ESMTP id lAGMYobV014675; Fri, 16 Nov 2007 17:34:50 -0500 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 lAGMYnv2028410; Fri, 16 Nov 2007 17:34:49 -0500 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 lAGMYHRO032318; Fri, 16 Nov 2007 17:34:49 -0500 Received: from ton.toronto.redhat.com (ton.yyz.redhat.com [10.15.16.15]) by touchme.toronto.redhat.com (Postfix) with ESMTP id 9125B8001FF; Fri, 16 Nov 2007 17:34:00 -0500 (EST) 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 lAGMXipR015108; Fri, 16 Nov 2007 17:33:44 -0500 Received: (from fche@localhost) by ton.toronto.redhat.com (8.13.1/8.13.1/Submit) id lAGMXilv015107; Fri, 16 Nov 2007 17:33:44 -0500 Date: Fri, 16 Nov 2007 22:35:00 -0000 From: "Frank Ch. Eigler" To: Mathieu Desnoyers Cc: ltt-dev@shafik.org, Systemtap List Subject: Re: patches to actually use markers? Message-ID: <20071116223344.GG25326@redhat.com> References: <20071029220454.GB4233@Krystal> <4728AD5F.1010604@redhat.com> <473DEBB7.40607@redhat.com> <20071116192415.GA25794@Krystal> <20071116201015.GA29545@Krystal> <20071116202645.GB25326@redhat.com> <20071116203539.GA32261@Krystal> <20071116204149.GD25326@redhat.com> <20071116220314.GA3197@Krystal> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20071116220314.GA3197@Krystal> User-Agent: Mutt/1.4.1i 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: 2007-q4/txt/msg00366.txt.bz2 Hi - On Fri, Nov 16, 2007 at 05:03:14PM -0500, Mathieu Desnoyers wrote: > [...] > We currently have three distinct events for a system call : > > syscall entry, with syscall id and instruction pointer > the syscall specific instrumentation (opt) > syscall exit > [...] Instrumentation within the syscall specific function helps > knowing when/if the operation has really been done _within the > kernel_. [...] Not just that - but *what* the actual operation was. > [...] Given these two opposite sets of constraints, I think having > more than one instrumentation site per syscall makes sense. Sure - what bothers me is the satisfaction with the inconsistency of some system calls having no specific markers. > Moreover, markers are really cheap... :) I'm not the one who must buy what we're selling - it's the kernel maintainers. :-) > [...] Yes, refcount would be the way to go. The code is currently > in kernel/sched.c, since it touches the threads. I would have to add > the refcount. It will be in the next LTTng prerelease. But you see, if markers are not just really cheap but really really cheap, then you don't need the task flag, nor the new API for refcounting the flags' clients, nor the new machinery to propagate the flag to new tasks. You just put unconditional markers in there and let the possible multiple marker handlers do their own filtering. - FChE