Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S268300AbUIBNSp (ORCPT ); Thu, 2 Sep 2004 09:18:45 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S268306AbUIBNSo (ORCPT ); Thu, 2 Sep 2004 09:18:44 -0400 Received: from dfw-gate1.raytheon.com ([199.46.199.230]:17218 "EHLO dfw-gate1.raytheon.com") by vger.kernel.org with ESMTP id S268300AbUIBNSa (ORCPT ); Thu, 2 Sep 2004 09:18:30 -0400 Subject: Re: [patch] voluntary-preempt-2.6.9-rc1-bk4-Q7 To: Ingo Molnar Cc: "K.R. Foley" , linux-kernel@vger.kernel.org, Lee Revell , Thomas Charbonnel X-Mailer: Lotus Notes Release 5.0.8 June 18, 2001 Message-ID: From: Mark_H_Johnson@raytheon.com Date: Thu, 2 Sep 2004 08:18:02 -0500 X-MIMETrack: Serialize by Router on RTSHOU-DS01/RTS/Raytheon/US(Release 6.5.2|June 01, 2004) at 09/02/2004 08:18:04 AM MIME-Version: 1.0 Content-type: text/plain; charset=US-ASCII X-SPAM: 0.00 Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1636 Lines: 45 >(you mean 500+ usec, correct?) > >there's no way the scheduler can have 500 usecs of overhead going from >dequeue_task() to __switch_to(): we have all interrupts disabled and >take zero locks! This is almost certainly some hardware effect (i >described some possibilities and tests a couple of mails earlier). > >In any case, please enable nmi_watchdog=1 so that we can see (in -Q7) >what happens on the other CPUs during such long delays. Booted with nmi_watchdog=1, saw the kernel message indicating that NMI was checked OK. The first trace looks something like this... latency 518 us, entries: 79 ... started at schedule+0x51/0x740 ended at schedule+0x337/0x740 00000001 0.000ms (+0.000ms): schedule (io_schedule) 00000001 0.000ms (+0.000ms): sched_clock (schedule) 00010001 0.478ms (+0.478ms): do_nmi (sched_clock) 00010001 0.478ms (+0.000ms): do_nmi (<08049b21>) 00010001 0.482ms (+0.003ms): profile_tick (nmi_watchdog_tick) ... and a few entries later ends up at do_IRQ (sched_clock). The second trace goes from dequeue_task to __switch_to with a similar pattern - the line with do_nmi has +0.282ms duration and the line notifier_call_chain (profile_hook) as +0.135ms duration. I don't see how this provides any additional information but will provide several additional traces when the test gets done in a few minutes. --Mark H Johnson - 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/