From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S261769AbTJRR5a (ORCPT ); Sat, 18 Oct 2003 13:57:30 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S261773AbTJRR5a (ORCPT ); Sat, 18 Oct 2003 13:57:30 -0400 Received: from fw.osdl.org ([65.172.181.6]:28650 "EHLO mail.osdl.org") by vger.kernel.org with ESMTP id S261769AbTJRR5Z (ORCPT ); Sat, 18 Oct 2003 13:57:25 -0400 Date: Sat, 18 Oct 2003 10:57:33 -0700 From: Andrew Morton To: Adrian Bunk Cc: mbligh@aracnet.com, linux-kernel@vger.kernel.org Subject: Re: [2.6 patch] add a config option for -Os compilation Message-Id: <20031018105733.380ea8d2.akpm@osdl.org> In-Reply-To: <20031018174434.GJ12423@fs.tum.de> References: <20031015225055.GS17986@fs.tum.de> <20031015161251.7de440ab.akpm@osdl.org> <20031015232440.GU17986@fs.tum.de> <20031015165205.0cc40606.akpm@osdl.org> <20031018102127.GE12423@fs.tum.de> <649730000.1066491920@[10.10.2.4]> <20031018102402.3576af6c.akpm@osdl.org> <20031018174434.GJ12423@fs.tum.de> X-Mailer: Sylpheed version 0.9.4 (GTK+ 1.2.10; i686-pc-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Adrian Bunk wrote: > > On Sat, Oct 18, 2003 at 10:24:02AM -0700, Andrew Morton wrote: > > "Martin J. Bligh" wrote: > > > > > > Please don't - I benchmarked it a while ago, and it's definitely slower. > > > > Alan said he generally found -Os to be faster... > > Not exactly: > http://www.ussg.iu.edu/hypermail/linux/kernel/0211.0/1513.html > http://www.ussg.iu.edu/hypermail/linux/kernel/0308.1/1261.html And bear in mind that you can see significant changes in benchmark results between equivalent kernels even when the optimisation level is kept the same, due to aliasing and alignment luck. It would take a quite a lot of work to measure this properly. A simple A/B comparison doesn't cut it.