Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1758808Ab1E0KFY (ORCPT ); Fri, 27 May 2011 06:05:24 -0400 Received: from cam-admin0.cambridge.arm.com ([217.140.96.50]:52204 "EHLO cam-admin0.cambridge.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753260Ab1E0KFX (ORCPT ); Fri, 27 May 2011 06:05:23 -0400 Subject: Re: [PATCH] ARM: Do not allow unaligned accesses when CONFIG_ALIGNMENT_TRAP From: Will Deacon To: Andi Kleen Cc: Nicolas Pitre , Catalin Marinas , =?ISO-8859-1?Q?M=E5ns_Rullg=E5rd?= , linux-arm-kernel@lists.infradead.org, lkml , Andrew Morton , sam@ravnborg.org In-Reply-To: <4DDEC1C0.20807@linux.intel.com> References: <20110523111648.10474.78396.stgit@e102109-lin.cambridge.arm.com> <20110523132124.GI17672@n2100.arm.linux.org.uk> <1306229953.19557.14.camel@e102109-lin.cambridge.arm.com> <20110524171331.GA2941@arm.com> <20110525111405.GA12010@e102109-lin.cambridge.arm.com> <20110525124348.GA2340@arm.com> <1306429854.26735.9.camel@e102144-lin.cambridge.arm.com> <4DDEC1C0.20807@linux.intel.com> Content-Type: text/plain; charset="UTF-8" Date: Fri, 27 May 2011 11:05:09 +0100 Message-ID: <1306490709.26257.4.camel@e102144-lin.cambridge.arm.com> Mime-Version: 1.0 X-Mailer: Evolution 2.28.1 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1223 Lines: 30 Hi Andi, On Thu, 2011-05-26 at 22:10 +0100, Andi Kleen wrote: > > > It is possible that -fconserve-stack is still valuable on ARM given that > > it is also used with -mno-unaligned-access for other things than > > structure packing on the stack, and therefore its merits can be debated > > independently from the alignment issue at hand. > > The big advantage of -fconserve-stack is that it throttles the inliner > if the inlining > would cause too much stack growth. This is something you likely want > on ARM too, especially as code gets more and more complex. Do you have any concrete examples of -fconserve-stack giving an overall win that isn't in the noise? The fact that the GCC documentation explicitly states that enabling the option can lead to `making the program slower' does make me question why we're enabling it in the first place. >From private conversation, the GCC guys don't seem to think this is a bug so I'm reluctant to open a bugzilla ticket. Will -- 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/