From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757464AbXKWMWa (ORCPT ); Fri, 23 Nov 2007 07:22:30 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1756209AbXKWMWW (ORCPT ); Fri, 23 Nov 2007 07:22:22 -0500 Received: from atrey.karlin.mff.cuni.cz ([195.113.31.123]:58298 "EHLO atrey.karlin.mff.cuni.cz" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755601AbXKWMWV (ORCPT ); Fri, 23 Nov 2007 07:22:21 -0500 Date: Fri, 23 Nov 2007 13:22:54 +0100 From: Pavel Machek To: Thomas Gleixner Cc: Ingo Molnar , kernel list Subject: Re: nohz and strange sleep latencies Message-ID: <20071123122254.GC2055@elf.ucw.cz> References: <20071119203152.GA1772@elf.ucw.cz> <20071119205555.GA28696@elte.hu> <20071119211142.GA1857@elf.ucw.cz> <20071120085704.GA19950@elte.hu> <20071120105458.GA1597@elf.ucw.cz> <20071120205454.GD10008@elte.hu> <20071120225246.GA24380@elte.hu> <20071122185238.GA1821@elf.ucw.cz> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-Warning: Reading this can be dangerous to your mental health. User-Agent: Mutt/1.5.16 (2007-06-11) Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Hi! > > > but perhaps somehow we miss this fact and fail to turn off the lapic > > > clockevents drivers? > > > > Ok, I guess I'm lost. If I offline second CPU, I immediately get > > 1000Hz timer tick... is that expected? > > Hmm. No. I have no idea why this is happening. > > 34196 total events, 55.083 events/sec > echo 0 >/sys/devices/system/cpu/cpu1/online > 36073 total events, 54.679 events/sec Strange. > > I'm trying to decide when system is idle (lets say that means "no user > > task is scheduled to wakeup within 10 seconds)... I added some > > instrumentation to nohz subsystem, but it does not behave like I'd > > expect: even if I run "while true; do sleep .01; done" loop, I see > > nohz preparing for 5 seconds sleep... while it seems obvious that it > > can only be 10msec sleep, and with max_cstate=1, it works that > > way... Plus, nte->start_pid seems to contain some random numbers :-(. > > > > What am I doing wrong? > > > > (Patch for illustration, I can generate full diff against vanilla, > > but...) > > Just to make sure what we are hunting: Do you have the same problem > with an non-pavel-tainted 2.6.24-rc3 ? The strange sleep latencies were definitely there, I'll check for "offline cpu and get 1000 interrupts", too. Pavel -- (english) http://www.livejournal.com/~pavelmachek (cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html