Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757034Ab0FJN0X (ORCPT ); Thu, 10 Jun 2010 09:26:23 -0400 Received: from one.firstfloor.org ([213.235.205.2]:56669 "EHLO one.firstfloor.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752940Ab0FJN0W (ORCPT ); Thu, 10 Jun 2010 09:26:22 -0400 Date: Thu, 10 Jun 2010 15:26:16 +0200 From: Andi Kleen To: Ingo Molnar Cc: Peter Zijlstra , Jason Baron , linux-kernel@vger.kernel.org, mathieu.desnoyers@polymtl.ca, hpa@zytor.com, tglx@linutronix.de, rostedt@goodmis.org, andi@firstfloor.org, roland@redhat.com, rth@redhat.com, mhiramat@redhat.com, fweisbec@gmail.com, avi@redhat.com, davem@davemloft.net, vgoyal@redhat.com, sam@ravnborg.org Subject: Re: [PATCH 03/13] jump label v9: x86 support Message-ID: <20100610132616.GA19561@basil.fritz.box> References: <1276171930.2077.200.camel@twins> <20100610121440.GA20130@elte.hu> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20100610121440.GA20130@elte.hu> User-Agent: Mutt/1.5.17 (2007-11-01) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1277 Lines: 34 On Thu, Jun 10, 2010 at 02:14:40PM +0200, Ingo Molnar wrote: > > * Peter Zijlstra wrote: > > > On Wed, 2010-06-09 at 17:39 -0400, Jason Baron wrote: > > > + select HAVE_ARCH_JUMP_LABEL if !CC_OPTIMIZE_FOR_SIZE > > > > That deserves a comment somewhere, it basically makes OPTIMIZE_FOR_SIZE > > useless... > > Hm, we need more than a comment for that - distros enable CC_OPTIMIZE_FOR_SIZE > all the time, for the massive kernel image (and hotpath cache footprint) > savings. Is this fixable? Actually the big distros (RHEL, SLES) disable it all the time now. It costs you in some benchmarks. The code generated by -Os is often terrible. Nearly everytime I investigate some bad asm code being generated by gcc it goes away when that flag is disabled. A much better to get smaller kernel images is to do more __cold annotations for slow paths. Newer gcc will then simply only do -Os for these functions. It's already done for __init. -Andi -- ak@linux.intel.com -- Speaking for myself only. -- 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/