From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754176AbXGGCZY (ORCPT ); Fri, 6 Jul 2007 22:25:24 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1754109AbXGGCY5 (ORCPT ); Fri, 6 Jul 2007 22:24:57 -0400 Received: from emailhub.stusta.mhn.de ([141.84.69.5]:53197 "EHLO mailhub.stusta.mhn.de" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1753991AbXGGCY4 (ORCPT ); Fri, 6 Jul 2007 22:24:56 -0400 Date: Sat, 7 Jul 2007 04:25:26 +0200 From: Adrian Bunk To: Mathieu Desnoyers Cc: Chuck Ebbert , Andi Kleen , Andrew Morton , Alexey Dobriyan , linux-kernel@vger.kernel.org, mbligh@google.com Subject: Re: [patch 10/10] Scheduler profiling - Use immediate values Message-ID: <20070707022526.GC3492@stusta.de> References: <20070703164046.645090494@polymtl.ca> <20070703164516.377240547@polymtl.ca> <20070703181151.GB5800@martell.zuzino.mipt.ru> <20070703185748.GA4047@Krystal> <20070705132120.8edbc1f3.akpm@linux-foundation.org> <468EBEB2.4070605@redhat.com> <20070706232843.GT3492@stusta.de> <20070706234315.GA19804@Krystal> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <20070706234315.GA19804@Krystal> 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 Fri, Jul 06, 2007 at 07:43:15PM -0400, Mathieu Desnoyers wrote: > * Adrian Bunk (bunk@stusta.de) wrote: > > On Fri, Jul 06, 2007 at 06:14:10PM -0400, Chuck Ebbert wrote: > > > On 07/06/2007 07:44 AM, Andi Kleen wrote: > > > > I think the optimization is a good idea, although i dislike it > > > > that it is complicated for the dynamic markers. If it was just > > > > static it would be much simpler. > > > > > > Another thing to consider is that there might be hundreds of these > > > probes/tracepoints active in an instrumented kernel. The overhead > > > adds up fast, so the gain may be worth all the pain. > > > > Only if you want to squeeze the last bit of performance out of > > _debugging_ functionality. > > > > You avoid all the pain if you simply don't use debugging functionality > > on production systems. > > > > Adrian, > > Please have a look at my markers posts, especially: > > http://www.ussg.iu.edu/hypermail/linux/kernel/0707.0/0669.html > > And also look into OLS 2007 proceedings for Martin Bligh's paper on > Debugging Google sized clusters. It basically makes the case for adding > functionnality to debug _user space_ problems on production systems that > can be turned on dynamically. Using a different kernel for tracing still fulfills all the requirements listed in section 5 of your paper... > Mathieu 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