Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932360Ab0AOUha (ORCPT ); Fri, 15 Jan 2010 15:37:30 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1758258Ab0AOUh0 (ORCPT ); Fri, 15 Jan 2010 15:37:26 -0500 Received: from mail.gmx.net ([213.165.64.20]:34457 "HELO mail.gmx.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with SMTP id S1758256Ab0AOUhW (ORCPT ); Fri, 15 Jan 2010 15:37:22 -0500 X-Authenticated: #4463548 X-Provags-ID: V01U2FsdGVkX19gW1lW36FgyyR9a0sjYDnh3pOf9RjwTwfpEyVZqX bRJ4H5eg3Iaadb Date: Fri, 15 Jan 2010 22:40:39 +0200 (EET) From: Dimitrios Apostolou X-X-Sender: jimis@localhost.localdomain To: Pavel Machek cc: Arjan van de Ven , Alex Chiang , Len Brown , Bjorn Helgaas , Andrew Morton , Yinghai Lu , linux-kernel@vger.kernel.org Subject: Re: -O0 kernel Re: High cpu temperature with 2.6.32, bisection shows commit 69d258 (fwd) In-Reply-To: <20100115195811.GB1345@ucw.cz> Message-ID: References: <20100108171513.GB22713@ldl.fc.hp.com> <20100109134352.3dedd4ea@infradead.org> <20100109160836.26a344a9@infradead.org> <20100115195811.GB1345@ucw.cz> User-Agent: Alpine 2.00 (LNX 1167 2008-08-23) MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII; format=flowed X-Y-GMX-Trusted: 0 X-FuHaFi: 0.59999999999999998 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, 15 Jan 2010, Pavel Machek wrote: > >> BTW, how can I remove that irritating -O2 flag? I 'm used to compiling >> with -O0 my debug builds in userland, because compilation is *many times* >> faster. I should be really useful for bisections. > > Actually, figuring out kernel flags for fastest kernel compilation > would be nice. Nice for bisect, and nice for slow machines. Zaurus > needs 4 hours to compile kernel, kohjinsha cca 1.5 hours. > > -O0 may not fly, as inlining is needed... some tests are I did some research too and this has been discussed again. Regarding inlining and -O0 I understand that theoretically it should work, but practically it doesn't. Here is an explanatory message from Andi Kleen: http://lists.openwall.net/linux-kernel/2008/09/09/399 > neccessary. Now that we support icc, gcc -O0 should be doable, too... > > ...ok, so I tried -O0. > > -O2 compilation took 1250seconds, -O0 took 1167seconds and failed. > > is there some fast compiler around that could be used? Strange that -O0 was not faster. Compiling userland I'm sure I've seen great speeds, and much less memory usage. Another compiler that is infamous for its speed is TCC (Tiny C Compiler) but I haven't actually used it, perhaps you want to try first. :-) Dimitris -- 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/