From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756858AbYIRP6q (ORCPT ); Thu, 18 Sep 2008 11:58:46 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1754219AbYIRP6d (ORCPT ); Thu, 18 Sep 2008 11:58:33 -0400 Received: from terminus.zytor.com ([198.137.202.10]:45910 "EHLO terminus.zytor.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753477AbYIRP6c (ORCPT ); Thu, 18 Sep 2008 11:58:32 -0400 Message-ID: <48D27A7E.8090403@zytor.com> Date: Thu, 18 Sep 2008 08:57:50 -0700 From: "H. Peter Anvin" User-Agent: Thunderbird 2.0.0.16 (X11/20080723) MIME-Version: 1.0 To: Jason Baron CC: Ingo Molnar , Andrew Morton , Yinghai Lu , Thomas Gleixner , linux-kernel@vger.kernel.org Subject: Re: [PATCH 0/6] loglevel=pci:8,acpi:8,apic=8 support v6 References: <1221640067-24389-1-git-send-email-yhlu.kernel@gmail.com> <20080917015543.27172da4.akpm@linux-foundation.org> <20080917092732.GB32107@elte.hu> <20080917184618.GB6486@redhat.com> <48D159A7.5080907@zytor.com> <20080918105728.GF20967@elte.hu> <48D2758B.1000004@zytor.com> <20080918155041.GB3097@redhat.com> In-Reply-To: <20080918155041.GB3097@redhat.com> Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Jason Baron wrote: > > if we take this argument to its extreme, then we end up spending all of > our time verifying that the kernel is working correctly and no time > actually doing work. I think 'printk_ratelimit' captures this. Thus, the line > has to be drawn somewhere. If you want the messages in 'dmesg' use, > printk(KERN_DEBUG), and 'grep'. For the rest, I propose pre-filtering, which is > what 'dynamic debug' uses. > Taking any argument to its extreme and you come up with something ridiculous. One could equally argue that if you have so many debugging messages that you have to prefilter for performance, you're so bloating your kernel that you need to stop. I find it highly questionable that it makes sense to put even skipped messages into hot paths in the production kernel. Skipped prints are NOT free, even if they are lot cheaper than actually rendering the string. -hpa