Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S261954AbUKUMl0 (ORCPT ); Sun, 21 Nov 2004 07:41:26 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S261969AbUKUMlZ (ORCPT ); Sun, 21 Nov 2004 07:41:25 -0500 Received: from mx1.elte.hu ([157.181.1.137]:30945 "EHLO mx1.elte.hu") by vger.kernel.org with ESMTP id S261954AbUKUMlX (ORCPT ); Sun, 21 Nov 2004 07:41:23 -0500 Date: Sun, 21 Nov 2004 14:43:54 +0100 From: Ingo Molnar To: Florian Schmidt Cc: Lee Revell , linux-kernel@vger.kernel.org, Rui Nuno Capela , Mark_H_Johnson@Raytheon.com, "K.R. Foley" , Bill Huey , Adam Heath , Thomas Gleixner , Michal Schmidt , Fernando Pablo Lopez-Lezcano , Karsten Wiese , Gunther Persoons , emann@mrv.com, Shane Shrybman , Amit Shah Subject: Re: [patch] Real-Time Preemption, -RT-2.6.10-rc2-mm2-V0.7.29-0 Message-ID: <20041121134354.GA17759@elte.hu> References: <20041118123521.GA29091@elte.hu> <20041118164612.GA17040@elte.hu> <1100920963.1424.1.camel@krustophenia.net> <20041120125536.GC8091@elte.hu> <1100971141.6879.18.camel@krustophenia.net> <20041120191403.GA16262@elte.hu> <1100975745.6879.35.camel@krustophenia.net> <20041120201155.6dc43c39@mango.fruits.de> <20041120214035.2deceaeb@mango.fruits.de> <20041121125439.GA8224@elte.hu> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20041121125439.GA8224@elte.hu> User-Agent: Mutt/1.4.1i X-ELTE-SpamVersion: MailScanner 4.31.6-itk1 (ELTE 1.2) SpamAssassin 2.63 ClamAV 0.73 X-ELTE-VirusStatus: clean X-ELTE-SpamCheck: no X-ELTE-SpamCheck-Details: score=-4.9, required 5.9, autolearn=not spam, BAYES_00 -4.90 X-ELTE-SpamLevel: X-ELTE-SpamScore: -4 Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1350 Lines: 42 > * Florian Schmidt wrote: > > > Hmm, the max jitter rtc_wakeup shows at 1024hz is around 150us. Which > > seems a tiny bit large, too, as the rtc histogram shows a max wakeup > > latency of 16us.. > > yep, that's a bit too large too. What type of load does it need to > trigger such a 150 usec delay reliably? on a 2 GHz UP box the worst-case max jitter i can trigger via rtc_wakeup is 11 usecs, using the -5 kernel. The workload i used was 40 parallel copies of LTP plus a few hackbench runs. This is how i started rtc_wakeup: chrt -f 80 -p `pidof 'IRQ 0'` chrt -f 98 -p `pidof 'IRQ 8'` cd rtc_wakeup ./rtc_wakeup -f 1024 -t 100000 i.e. IRQ0 is below IRQ8 and the rtc_wakeup threads, but above every other IRQ thread. Here's the histogram of a short (~5 minutes) run: 1 247383 2 34842 3 1488 4 3188 5 125 6 1 so this a 6 usecs max delay measured by /dev/rtc. So on your box, if the max histogram delay was 16 usecs, i'd not expect a worse than ~30 usecs jitter measured by rtc_wakeup. Can you reproduce the 150 usecs jitter with the above IRQ setup? Ingo - 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/