Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756271AbYJWLQ0 (ORCPT ); Thu, 23 Oct 2008 07:16:26 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1752955AbYJWLQR (ORCPT ); Thu, 23 Oct 2008 07:16:17 -0400 Received: from lizzard.sbs.de ([194.138.37.39]:20107 "EHLO lizzard.sbs.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753157AbYJWLQR (ORCPT ); Thu, 23 Oct 2008 07:16:17 -0400 Message-ID: <49005CD0.2070807@siemens.com> Date: Thu, 23 Oct 2008 13:15:28 +0200 From: Jan Kiszka User-Agent: Mozilla/5.0 (X11; U; Linux i686 (x86_64); de; rv:1.8.1.12) Gecko/20080226 SUSE/2.0.0.12-1.1 Thunderbird/2.0.0.12 Mnenhy/0.7.5.666 MIME-Version: 1.0 To: Steven Rostedt CC: linux-kernel@vger.kernel.org, Ingo Molnar , Frederic Weisbecker , Abhishek Sagar , "David S. Miller" , Thomas Gleixner , Peter Zijlstra , Andrew Morton , Linus Torvalds , Steven Rostedt Subject: Re: [PATCH 08/13 v2] ftrace: do not trace init sections References: <20081022212721.167005680@goodmis.org> <20081022213552.440512191@goodmis.org> In-Reply-To: <20081022213552.440512191@goodmis.org> Content-Type: text/plain; charset=ISO-8859-15 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1129 Lines: 32 Steven Rostedt wrote: > The recordmcount script is now robust enough not to process any sections > but the .text section. But the gcc compiler still adds a call to mcount. > > Note: The function mcount looks like: > > ENTRY(mcount) > ret > END(mcount) > > Which means the overhead is just a return. > > This patch adds notrace to the init sections to not even bother calling > mcount (which simply returns). Sorry for a potentially dumb question (didn't follow all recent ftrace developments), but doesn't this mean that code in such sections is now invisible for all tracers, even with dynamic tracing disabled (in which case they should cause no problem)? What if you *do* want to have such functions in your trace as they may contribute to problem or give other useful hints? Jan -- Siemens AG, Corporate Technology, CT SE 2 Corporate Competence Center Embedded Linux -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/