From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from bombadil.infradead.org ([18.85.46.34]:35340 "EHLO bombadil.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752370AbZBWLLm (ORCPT ); Mon, 23 Feb 2009 06:11:42 -0500 Subject: Re: [PATCH] tracing/markers: make markers select tracepoints From: Peter Zijlstra In-Reply-To: <20090222122424.GA9951@redhat.com> References: <499edf47.1818d00a.060b.2b8d@mx.google.com> <499EE162.4050008@oracle.com> <20090220172241.GF24538@elte.hu> <1235302980.4632.8.camel@laptop> <1235304876.4632.10.camel@laptop> <20090222122424.GA9951@redhat.com> Content-Type: text/plain Date: Mon, 23 Feb 2009 12:11:27 +0100 Message-Id: <1235387487.4645.28.camel@laptop> Mime-Version: 1.0 Content-Transfer-Encoding: 7bit Sender: linux-kbuild-owner@vger.kernel.org List-ID: To: "Frank Ch. Eigler" Cc: Ingo Molnar , Randy Dunlap , Frederic Weisbecker , Steven Rostedt , linux-kernel@vger.kernel.org, zippel@linux-m68k.org, linux-kbuild@vger.kernel.org On Sun, 2009-02-22 at 07:24 -0500, Frank Ch. Eigler wrote: > Hi - > > On Sun, Feb 22, 2009 at 01:14:36PM +0100, Peter Zijlstra wrote: > > > > I would like to never merge an ftrace_printk() user... just as I'd like > > > > to get rid of every marker. > > > > > > But why? They solve a problem well enough that Ingo had in effect > > > reinvented them on Friday. > > > > Because after a printk() debug spree, I don't commit them, I toss them > > out and keep the fix. > > Markers solve a problem closer to tracepoints than to debugging > printk's. Not so. In both cases the regular stuff (NMI trace, OOPS, function/graph/sched trace, etc) is not enough and you wish to augment its output. > In this context, the main difference between tracepoints is that > markers need almost no hand-written glue code of the sort that make up > ftrace engines that just trace simple values. Simpler & smaller code > for the same output seems like a win. Right, for dumb tracers that's true I suppose, however any high-bandwidth tracer will try to avoid putting silly ASCII strings in and will therefore need to write more glue code. Which reduces these default thingies to printk() level debugging.