From owner-freebsd-current@FreeBSD.ORG Sat Dec 24 10:18:36 2011 Return-Path: Delivered-To: freebsd-current@freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:4f8:fff6::34]) by hub.freebsd.org (Postfix) with ESMTP id 0A5CC106566C for ; Sat, 24 Dec 2011 10:18:36 +0000 (UTC) (envelope-from matthias.andree@gmx.de) Received: from mailout-de.gmx.net (mailout-de.gmx.net [213.165.64.23]) by mx1.freebsd.org (Postfix) with SMTP id 491318FC13 for ; Sat, 24 Dec 2011 10:18:34 +0000 (UTC) Received: (qmail invoked by alias); 24 Dec 2011 09:51:52 -0000 Received: from g225199079.adsl.alicedsl.de (EHLO mandree.no-ip.org) [92.225.199.79] by mail.gmx.net (mp003) with SMTP; 24 Dec 2011 10:51:52 +0100 X-Authenticated: #428038 X-Provags-ID: V01U2FsdGVkX1+N5tY99+mNVr4mgiiIlj+DpVH6JLYOQTTwMtL0l2 mzEnUNHb+FZp8f Received: from [127.0.0.1] (localhost.localdomain [127.0.0.1]) by apollo.emma.line.org (Postfix) with ESMTP id 3499A23CE8F for ; Sat, 24 Dec 2011 10:51:51 +0100 (CET) Message-ID: <4EF5A0B7.8050002@gmx.de> Date: Sat, 24 Dec 2011 10:51:51 +0100 From: Matthias Andree User-Agent: Mozilla/5.0 (X11; U; Linux x86_64; en-US; rv:1.9.2.24) Gecko/20111109 Mnenhy/0.8.3 Thunderbird/3.1.16 MIME-Version: 1.0 To: freebsd-current@freebsd.org References: <20111223235642.GA37495@freebsd.org> In-Reply-To: <20111223235642.GA37495@freebsd.org> X-Enigmail-Version: 1.1.2 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit X-Y-GMX-Trusted: 0 Subject: Re: [rfc] removing -mpreferred-stack-boundary=2 flag for i386? X-BeenThere: freebsd-current@freebsd.org X-Mailman-Version: 2.1.5 Precedence: list List-Id: Discussions about the use of FreeBSD-current List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Sat, 24 Dec 2011 10:18:36 -0000 Am 24.12.2011 00:56, schrieb Alexander Best: > hi there, > > is -mpreferred-stack-boundary=2 really necessary for i386 builds any longer? > i built GENERIC (including modules) with and without that flag. the results > are: > > 1654496 bytes with the flag set > vs. > 1654952 bytes with the flag unset > > the gcc(1) man page states the following: > > " > This extra alignment does consume extra stack space, and generally > increases code size. Code that is sensitive to stack space usage, > such as embedded systems and operating system kernels, may want to > reduce the preferred alignment to -mpreferred-stack-boundary=2. > " > What do the numbers above have to do with *stack* alignment or size (which is a run-time figure, and cannot be statically determined if any variable-depth recursion takes place). What are those 16... numbers, anyways? How did you obtain them?