Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1750857AbWEMJUn (ORCPT ); Sat, 13 May 2006 05:20:43 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1750847AbWEMJUn (ORCPT ); Sat, 13 May 2006 05:20:43 -0400 Received: from mail.gmx.de ([213.165.64.20]:54210 "HELO mail.gmx.net") by vger.kernel.org with SMTP id S1750803AbWEMJUn (ORCPT ); Sat, 13 May 2006 05:20:43 -0400 X-Authenticated: #4399952 Date: Sat, 13 May 2006 11:20:39 +0200 From: Florian Paul Schmidt To: Darren Hart Cc: lkml , Ingo Molnar , Thomas Gleixner Subject: Re: rt20 scheduling latency testcase and failure data Message-ID: <20060513112039.41536fb5@mango.fruits> In-Reply-To: <200605121924.53917.dvhltc@us.ibm.com> References: <200605121924.53917.dvhltc@us.ibm.com> X-Mailer: Sylpheed-Claws 1.0.5 (GTK+ 1.2.10; i486-pc-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit X-Y-GMX-Trusted: 0 Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2266 Lines: 61 On Fri, 12 May 2006 19:24:53 -0700 Darren Hart wrote: > The test case emulates a periodic thread that wakes up on time%PERIOD=0, so > rather than sleeping the same amount of time each round, it checks now > against the start of its next period and sleeps for that length of time. > Every so often it will miss it's period, I've captured that data and included > a few of the interesting bits below. The results are from a run with a > period of 5ms, although I have seen them with periods as high as 17ms. The > system was under heavy network load for some of the time, but not all. [snip] > I'd appreciate any feedback on the test case, and in particular suggestions on > how I can go about determining where this lost time is being spent. There's a multitude of ways how you can misconfigure your -rt system :) Tell us more about your setup. Hardware? Full preemption? High resolution timers? Priority setup? From your code i see you run at prio 98. What about the IRQ handlers? And the softirq's, too? Other software? Flo P.S.: I ran the test a few [20 or so] times and didn't get any failures of the sort you see. Even with a 1ms period: ~/downloads$ ./sched_latency_lkml ------------------------------- Scheduling Latency ------------------------------- Running 10000 iterations with a period of 1 ms Expected running time: 10 s ITERATION DELAY(US) MAX_DELAY(US) FAILURES --------- --------- ------------- -------- 10000 32 47 0 Start Latency: 305 us: FAIL Min Latency: 16 us: PASS Avg Latency: 29 us: PASS Max Latency: 47 us: PASS Failed Iterations: 0 ~/downloads$ uname -a Linux mango.fruits 2.6.16-rt20 #4 PREEMPT Wed May 10 12:53:39 CEST 2006 i686 GNU/Linux Ooops, i must admit i have the nvidia binary only kernel module loaded, but i suppose this wouldn't make a difference for the better ;) I got high resolution timers enabled and left the softirq threads at their defaults. -- Palimm Palimm! http://tapas.affenbande.org - 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/