Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755480AbZAIS7l (ORCPT ); Fri, 9 Jan 2009 13:59:41 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1754992AbZAIS72 (ORCPT ); Fri, 9 Jan 2009 13:59:28 -0500 Received: from mu-out-0910.google.com ([209.85.134.187]:3991 "EHLO mu-out-0910.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754890AbZAIS70 (ORCPT ); Fri, 9 Jan 2009 13:59:26 -0500 DomainKey-Signature: a=rsa-sha1; c=nofws; d=gmail.com; s=gamma; h=message-id:date:from:to:subject:cc:in-reply-to:mime-version :content-type:content-transfer-encoding:content-disposition :references; b=vHp/wMhPMptgQ1/o6eCA7jjT4wi41GCqcyxiStC0ujBW8X24/321A/YFx6QA0s2JSH rpDi+HEN5vdsJrPfU2Iy0/WpHX+SW+uaivzN57VkEdLCSKwPHAnpIWMpQky8CyEHwgiv 9BpEE9r5oEtrpSP+uUjhksZbMX0nuv1oOFleI= Message-ID: <84fc9c000901091059v65265413wda053d3ce5b0d17a@mail.gmail.com> Date: Fri, 9 Jan 2009 19:59:22 +0100 From: "Richard Guenther" To: "Andi Kleen" Subject: Re: [patch] measurements, numbers about CONFIG_OPTIMIZE_INLINING=y impact Cc: "Linus Torvalds" , "Matthew Wilcox" , "Dirk Hohndel" , "H. Peter Anvin" , "Ingo Molnar" , "jim owens" , "Chris Mason" , "Peter Zijlstra" , "Steven Rostedt" , paulmck@linux.vnet.ibm.com, "Gregory Haskins" , "Andrew Morton" , "Linux Kernel Mailing List" , linux-fsdevel , linux-btrfs , "Thomas Gleixner" , "Nick Piggin" , "Peter Morreale" , "Sven Dietrich" , jh@suse.cz In-Reply-To: <20090109181952.GI26290@one.firstfloor.org> MIME-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Content-Disposition: inline References: <20090109130057.GA31845@elte.hu> <20090109153508.GA4671@elte.hu> <49677CB1.3030701@zytor.com> <20090109084620.3c711aad@infradead.org> <20090109172011.GD26290@one.firstfloor.org> <20090109172801.GC6936@parisc-linux.org> <20090109174719.GG26290@one.firstfloor.org> <20090109173914.GD6936@parisc-linux.org> <20090109181952.GI26290@one.firstfloor.org> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1471 Lines: 29 On Fri, Jan 9, 2009 at 7:19 PM, Andi Kleen wrote: >> So we do have special issues. And exactly _because_ we have special issues >> we should also expect that some compiler defaults simply won't ever really >> be appropriate for us. > > I agree that the kernel needs quite different inlining heuristics > than let's say a template heavy C++ program. I guess that is > also where our trouble comes from -- gcc is more tuned for the > later. Perhaps because the C++ programmers are better at working > with the gcc developers? > > But it's also not inconceivable that gcc adds a -fkernel-inlining or > similar that changes the parameters if we ask nicely. I suppose > actually such a parameter would be useful for far more programs > than the kernel. I think that the kernel is a perfect target to optimize default -Os behavior for (whereas template heavy C++ programs are a target to optimize -O2 for). And I think we did a good job in listening to kernel developers if once in time they tried to talk to us - GCC 4.3 should be good in compiling the kernel with default -Os settings. We, unfortunately, cannot retroactively fix old versions that kernel developers happen to like and still use. Richard. -- 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/