Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751893AbZJWKh6 (ORCPT ); Fri, 23 Oct 2009 06:37:58 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1751657AbZJWKh5 (ORCPT ); Fri, 23 Oct 2009 06:37:57 -0400 Received: from mx2.mail.elte.hu ([157.181.151.9]:45582 "EHLO mx2.mail.elte.hu" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751402AbZJWKh5 (ORCPT ); Fri, 23 Oct 2009 06:37:57 -0400 Date: Fri, 23 Oct 2009 12:37:46 +0200 From: Ingo Molnar To: John Kacur Cc: Frederic Weisbecker , Steven Rostedt , Thomas Gleixner , linux-kernel@vger.kernel.org Subject: Re: [performance problem] CONFIG_DYNAMIC_FTRACE: Increased kernel build times Message-ID: <20091023103746.GF19169@elte.hu> References: <20091023074533.GA10067@elte.hu> <520f0cf10910230307k91d0c80sa3d69bcd74d6e1f1@mail.gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: User-Agent: Mutt/1.5.19 (2009-01-05) X-ELTE-SpamScore: 0.0 X-ELTE-SpamLevel: X-ELTE-SpamCheck: no X-ELTE-SpamVersion: ELTE 2.0 X-ELTE-SpamCheck-Details: score=0.0 required=5.9 tests=none autolearn=no SpamAssassin version=3.2.5 _SUMMARY_ Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1371 Lines: 41 * John Kacur wrote: > 2009/10/23 Ingo Molnar wrote: > > > > 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. > > Hi Ingo, do you still have the profiling data to share with us? [...] no finegrained info - i did a perf stat run. > [...] Was the problem more in objcopy / objdump, rather than in the > perl script itself? in top i saw perl pop up most of the time, that's where i'd suspect a good portion of the overhead. Ingo -- 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/