Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755555Ab2FWQtY (ORCPT ); Sat, 23 Jun 2012 12:49:24 -0400 Received: from mail-qa0-f46.google.com ([209.85.216.46]:47920 "EHLO mail-qa0-f46.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751613Ab2FWQtX (ORCPT ); Sat, 23 Jun 2012 12:49:23 -0400 MIME-Version: 1.0 In-Reply-To: <24bd04a1-1702-4d57-af64-af2381992789@email.android.com> References: <20120623161324.GS11413@one.firstfloor.org> <24bd04a1-1702-4d57-af64-af2381992789@email.android.com> Date: Sat, 23 Jun 2012 09:49:22 -0700 Message-ID: Subject: Re: PATCH] Use -mpreferred-stack-boundary=3 on x86-64 if supported From: "H.J. Lu" To: "H. Peter Anvin" Cc: Andi Kleen , LKML Content-Type: text/plain; charset=ISO-8859-1 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1092 Lines: 34 On Sat, Jun 23, 2012 at 9:17 AM, H. Peter Anvin wrote: > To keep gcc from paddong the stack to maintain a nonexistent alignment. > > Andi Kleen wrote: > >>> This patch uses -mpreferred-stack-boundary=3 on x86-64 if it is >>supported. >>> I have been running 3.4 kernel compiled with this option for weeks. >> >>But why? >> >>All the SSE code in the kernel should adjust manually. And the other >>code doesn't need it. >> >>Besides the entry points do not guarantee alignment. >> >>For the kernel it would be probably more useful to have a attribute >>per function that forces alignment. There was an attempt from you to do it in 2007: http://lkml.indiana.edu/hypermail/linux/kernel/0708.2/2604.html http://gcc.gnu.org/ml/gcc-patches/2007-07/msg01697.html But the gcc patch was never checked in. -- H.J. -- 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/