Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S266908AbUKAQDN (ORCPT ); Mon, 1 Nov 2004 11:03:13 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S269146AbUKAQDM (ORCPT ); Mon, 1 Nov 2004 11:03:12 -0500 Received: from 213-239-205-147.clients.your-server.de ([213.239.205.147]:58535 "EHLO debian.tglx.de") by vger.kernel.org with ESMTP id S267540AbUKAPzf (ORCPT ); Mon, 1 Nov 2004 10:55:35 -0500 Subject: Re: [Fwd: Re: [patch] Real-Time Preemption, -RT-2.6.9-mm1-V0.4] From: Thomas Gleixner Reply-To: tglx@linutronix.de To: Ingo Molnar Cc: Florian Schmidt , Lee Revell , Paul Davis , LKML , mark_h_johnson@raytheon.com, Bill Huey , Adam Heath , Michal Schmidt , Fernando Pablo Lopez-Lezcano , Karsten Wiese , jackit-devel , Rui Nuno Capela , "K.R. Foley" In-Reply-To: <20041101140630.GA20448@elte.hu> References: <20041031120721.GA19450@elte.hu> <20041031124828.GA22008@elte.hu> <1099227269.1459.45.camel@krustophenia.net> <20041031131318.GA23437@elte.hu> <20041031134016.GA24645@elte.hu> <20041031162059.1a3dd9eb@mango.fruits.de> <20041031165913.2d0ad21e@mango.fruits.de> <20041031200621.212ee044@mango.fruits.de> <20041101134235.GA18009@elte.hu> <20041101135358.GA19718@elte.hu> <20041101140630.GA20448@elte.hu> Content-Type: text/plain; charset=ISO-8859-1 Organization: linutronix Date: Mon, 01 Nov 2004 16:47:20 +0100 Message-Id: <1099324040.3337.32.camel@thomas> Mime-Version: 1.0 X-Mailer: Evolution 2.0.2 Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1480 Lines: 41 On Mon, 2004-11-01 at 15:06 +0100, Ingo Molnar wrote: > ah, found it. Only RT tasks were supposed to get special priority > handling, while in fact all tasks got it - so when Thomas ran hackbench > (Thomas, you did, right?) it created an O(nr_hackbench) overhead within > the mutex code ... I've uploaded -V0.6.5 to the usual place: Yes, I was running hackbench as usual > http://redhat.com/~mingo/realtime-preempt/ > > Thomas, can you confirm that this kernel fixes the irqs-off latencies? > (the priority loop indeed was done with irqs turned off.) The latencies are still there. I have the feeling it's worse than 0.6.2. It's definitely irq-off. I have a card with a controller, which produces an 2ms interrupt. The controller busy loops until the second level ack is done. The time is measured from raising the irq to the 2nd level ack. The irqhandler is using NODELAY and keeps irqs disabled. So the measured time in the controller is the irqs disabled time + the irq latency (which is ~7?s). The testrun on 0.6.5 showed latencies up to 600?s within 10 minutes. After 15 Mintes the keyboard was dead. I'm porting some of the Libertos debugging stuff into 0.6.5, so I can instrument the problem. More later. tglx - 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/