From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754076AbYI3SOw (ORCPT ); Tue, 30 Sep 2008 14:14:52 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1753240AbYI3SOk (ORCPT ); Tue, 30 Sep 2008 14:14:40 -0400 Received: from tomts36-srv.bellnexxia.net ([209.226.175.93]:58236 "EHLO tomts36-srv.bellnexxia.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753711AbYI3SOj (ORCPT ); Tue, 30 Sep 2008 14:14:39 -0400 X-IronPort-Anti-Spam-Filtered: true X-IronPort-Anti-Spam-Result: AhUFAJMI4khMQWq+/2dsb2JhbACBZL4hgWk Date: Tue, 30 Sep 2008 14:14:36 -0400 From: Mathieu Desnoyers To: Martin Bligh Cc: Steven Rostedt , Peter Zijlstra , linux-kernel@vger.kernel.org, prasad@linux.vnet.ibm.com, Linus Torvalds , Thomas Gleixner , od@suse.com, "Frank Ch. Eigler" , Andrew Morton , hch@lst.de, David Wilder , Tom Zanussi Subject: Re: [RFC PATCH] LTTng relay buffer allocation, read, write Message-ID: <20080930181436.GA19690@Krystal> References: <20080927134012.GA11930@Krystal> <1222535419.16700.300.camel@lappy.programming.kicks-ass.net> <20080929155004.GA11029@Krystal> <1222709445.23876.70.camel@twins.programming.kicks-ass.net> <20080929203124.GA23070@Krystal> <33307c790809301022q2821ecc7iabf41eb513707e0c@mail.gmail.com> <33307c790809301023v1b0755fbsab1bbfa9bfaad58@mail.gmail.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit Content-Disposition: inline In-Reply-To: <33307c790809301023v1b0755fbsab1bbfa9bfaad58@mail.gmail.com> X-Editor: vi X-Info: http://krystal.dyndns.org:8080 X-Operating-System: Linux/2.6.21.3-grsec (i686) X-Uptime: 14:13:15 up 117 days, 22:53, 8 users, load average: 0.53, 0.48, 0.63 User-Agent: Mutt/1.5.16 (2007-06-11) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org * Martin Bligh (mbligh@google.com) wrote: > On Tue, Sep 30, 2008 at 10:22 AM, Martin Bligh wrote: > >> A 4 byte dataless payload is useless anyway. > > > > Not at all convinced that's true - we used it for lots of things. > > Start and end of irq event is one frequent example. > > > > Also, in a compact mode, we can record start and end of > > syscalls like this (without parameters). > > Ah, sorry, maybe I misread this. No data with no event ids, etc > is fairly useless. 4 bytes data including space to record event ids is OK. In Steven's scheme, the event IDs in the 4 bytes are reserved for (useless) internal use ;) They can therefore not be used for specific tracer event IDs, which I think is a misuse of the precious bits otherwise available to store really useful event IDs. Mathieu -- Mathieu Desnoyers OpenPGP key fingerprint: 8CD5 52C3 8E3C 4140 715F BA06 3F25 A8FE 3BAE 9A68