Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756348AbXFYBqS (ORCPT ); Sun, 24 Jun 2007 21:46:18 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1752194AbXFYBqJ (ORCPT ); Sun, 24 Jun 2007 21:46:09 -0400 Received: from mailout.stusta.mhn.de ([141.84.69.5]:38873 "EHLO mailhub.stusta.mhn.de" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1752134AbXFYBqI (ORCPT ); Sun, 24 Jun 2007 21:46:08 -0400 Date: Mon, 25 Jun 2007 03:46:28 +0200 From: Adrian Bunk To: Jeff Garzik Cc: Arjan van de Ven , Benjamin LaHaise , Oleg Verych , rae l , linux-kernel@vger.kernel.org Subject: Re: -Os versus -O2 Message-ID: <20070625014627.GC1094@stusta.de> References: <91b13c310706240558p70dbaed2g570b57ab480aa974@mail.gmail.com> <20070624222518.GA10398@flower.upol.cz> <1182723318.6819.5.camel@laptopd505.fenrus.org> <20070624232314.GA971@kvack.org> <1182730156.6819.8.camel@laptopd505.fenrus.org> <20070625001203.GB971@kvack.org> <1182731022.6819.10.camel@laptopd505.fenrus.org> <20070625004106.GA1094@stusta.de> <467F1B8D.3080507@garzik.org> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <467F1B8D.3080507@garzik.org> User-Agent: Mutt/1.5.15+20070412 (2007-04-11) Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1248 Lines: 36 On Sun, Jun 24, 2007 at 09:34:05PM -0400, Jeff Garzik wrote: > Adrian Bunk wrote: >> The interesting questions are: >> Does -Os still sometimes generate faster code with gcc 4.2? >> If yes, why? > > Smaller code can mean fewer page faults, fewer cache invalidations, etc. > > It's not just a matter of compiler code generation, gotta look at the whole > picture. Sure, but my point is that if the kernel is considered special and the best optimization for the kernel is therefore between -Os and -O2, we should try to find this point of best optimization. This should address Arjans point that -Os might not be best choice for best performance (and it's actually our fault if gcc generates stupid but small code when we use -Os). > Jeff cu Adrian -- "Is there not promise of rain?" Ling Tan asked suddenly out of the darkness. There had been need of rain for many days. "Only a promise," Lao Er said. Pearl S. Buck - Dragon Seed - 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/