From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754645AbXGGR7X (ORCPT ); Sat, 7 Jul 2007 13:59:23 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1752868AbXGGR7L (ORCPT ); Sat, 7 Jul 2007 13:59:11 -0400 Received: from emailhub.stusta.mhn.de ([141.84.69.5]:53701 "EHLO mailhub.stusta.mhn.de" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1752721AbXGGR7J (ORCPT ); Sat, 7 Jul 2007 13:59:09 -0400 Date: Sat, 7 Jul 2007 19:59:39 +0200 From: Adrian Bunk To: Willy Tarreau Cc: "Frank Ch. Eigler" , Dave Jones , Chuck Ebbert , Andi Kleen , Andrew Morton , Mathieu Desnoyers , Alexey Dobriyan , linux-kernel@vger.kernel.org Subject: Re: [patch 10/10] Scheduler profiling - Use immediate values Message-ID: <20070707175939.GI3492@stusta.de> References: <20070703185748.GA4047@Krystal> <20070705132120.8edbc1f3.akpm@linux-foundation.org> <468EBEB2.4070605@redhat.com> <20070706232843.GT3492@stusta.de> <20070706233827.GC13125@redhat.com> <20070707001008.GV3492@stusta.de> <20070707170157.GH3492@stusta.de> <20070707172011.GB943@1wt.eu> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <20070707172011.GB943@1wt.eu> User-Agent: Mutt/1.5.16 (2007-06-11) Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org On Sat, Jul 07, 2007 at 07:20:12PM +0200, Willy Tarreau wrote: > On Sat, Jul 07, 2007 at 07:01:57PM +0200, Adrian Bunk wrote: > > On Sat, Jul 07, 2007 at 11:45:20AM -0400, Frank Ch. Eigler wrote: >... > > You always have to decide between some debug code and some small bit of > > performance. There's a reason why options to disable things like BUG() > > or printk() are in the kernel config menus hidden behind CONFIG_EMBEDDED > > although they obviously have some performance impact. > > It is not for the CPU performance they can be disabled, but for the code > size which is a real problem on embedded system. While you often have > mem/cpu_mhz ratios around 1GB/1GHz on servers and desktops, you more often > have ratios like 16MB/500MHz which is 1:32 of the former. That's why you > optimize for size at the expense of speed on such systems. The latter is not true for my two examples. CONFIG_PRINTK=n, CONFIG_BUG=n will obviously make the kernel both smaller and faster. [1] > Regards, > Willy cu Adrian [1] faster due to less code to execute and positive cache effects due to the smaller code [2] [2] whether the "faster" is big enough that it is in any way measurable is a different question -- "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