From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751552AbZJWHph (ORCPT ); Fri, 23 Oct 2009 03:45:37 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1751305AbZJWHph (ORCPT ); Fri, 23 Oct 2009 03:45:37 -0400 Received: from mx2.mail.elte.hu ([157.181.151.9]:44319 "EHLO mx2.mail.elte.hu" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751083AbZJWHpg (ORCPT ); Fri, 23 Oct 2009 03:45:36 -0400 Date: Fri, 23 Oct 2009 09:45:33 +0200 From: Ingo Molnar To: Steven Rostedt , =?iso-8859-1?Q?Fr=E9d=E9ric?= Weisbecker Cc: linux-kernel@vger.kernel.org, Thomas Gleixner Subject: [performance problem] CONFIG_DYNAMIC_FTRACE: Increased kernel build times Message-ID: <20091023074533.GA10067@elte.hu> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline User-Agent: Mutt/1.5.19 (2009-01-05) X-ELTE-SpamScore: -1.5 X-ELTE-SpamLevel: X-ELTE-SpamCheck: no X-ELTE-SpamVersion: ELTE 2.0 X-ELTE-SpamCheck-Details: score=-1.5 required=5.9 tests=BAYES_00 autolearn=no SpamAssassin version=3.2.5 -1.5 BAYES_00 BODY: Bayesian spam probability is 0 to 1% [score: 0.0000] Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Steve, i did an 64-bit allyesconfig build test (with debug_info disabled), with and without CONFIG_DYNAMIC_FTRACE set. The build time results are: -CONFIG_DYNAMIC_FTRACE: 266.30 +CONFIG_DYNAMIC_FTRACE: 296.07 (+11.2%) So we get more than 10% build time overhead. That's quite high - higher than what i remember having measured originally when the first iteration of the mcount code went in. This extra overhead comes from the mcount post-processing script (scripts/recordmcount.pl) that runs objcopy as well and is written in Perl. I think this whole angle needs to be improved - 10% is way too high of a price to pay. Ingo