From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S261158AbVFLEVG (ORCPT ); Sun, 12 Jun 2005 00:21:06 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S261870AbVFLEVG (ORCPT ); Sun, 12 Jun 2005 00:21:06 -0400 Received: from opersys.com ([64.40.108.71]:41992 "EHLO www.opersys.com") by vger.kernel.org with ESMTP id S261158AbVFLEVC (ORCPT ); Sun, 12 Jun 2005 00:21:02 -0400 Message-ID: <42ABBA95.3050602@opersys.com> Date: Sun, 12 Jun 2005 00:31:17 -0400 From: Karim Yaghmour Reply-To: karim@opersys.com Organization: Opersys inc. User-Agent: Mozilla/5.0 (X11; U; Linux i686; en-US; rv:1.7.2) Gecko/20040805 Netscape/7.2 X-Accept-Language: en-us, en, fr, fr-be, fr-ca, fr-fr MIME-Version: 1.0 To: Daniel Walker CC: Ingo Molnar , Esben Nielsen , linux-kernel@vger.kernel.org, sdietrich@mvista.com, Philippe Gerum Subject: Re: [PATCH] local_irq_disable removal References: In-Reply-To: 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 Daniel Walker wrote: > Interesting .. So "cli" takes 7 cycles , "sti" takes 7 cycles. The current > method does "lea" which takes 1 cycle, and "or" which takes 1 cycle. I'm > not sure if there is any function call overhead .. So the soft replacment > of cli/sti is 70% faster on a per instruction level .. So it's at least > not any slower .. Does everyone agree on that? The proof is in the pudding: it's not for nothing that the results we published earlier show that the mere enabling of Adeos actually increases Linux's performance under heavy load. This could easily be called the Stodolsky effect. Here, have a look at this article, it was presented at the USENIX Symposium on Microkernels and Other Kernel Architectures ... in 1993: http://www-2.cs.cmu.edu/afs/cs.cmu.edu/user/danner/www/OptSynch.ps We've been referring back to this paper as early as the first public release of Adeos ... in June 2002. That being said, I'm not sure exactly why you guys are reinventing the wheel. Adeos already does this soft-cli/sti stuff for you, it's been available for a few years already, tested, and ported to a number of architectures, and is generalized, why not just adopt it? After all, like I've been saying for some time, it isn't mutually exclusive with PREEMPT_RT. Karim -- Author, Speaker, Developer, Consultant Pushing Embedded and Real-Time Linux Systems Beyond the Limits http://www.opersys.com || karim@opersys.com || 1-866-677-4546