From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752390AbXKSVLX (ORCPT ); Mon, 19 Nov 2007 16:11:23 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1751293AbXKSVLP (ORCPT ); Mon, 19 Nov 2007 16:11:15 -0500 Received: from gprs189-60.eurotel.cz ([160.218.189.60]:45167 "EHLO amd.ucw.cz" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1751244AbXKSVLO (ORCPT ); Mon, 19 Nov 2007 16:11:14 -0500 Date: Mon, 19 Nov 2007 22:11:42 +0100 From: Pavel Machek To: Ingo Molnar Cc: kernel list , tglx@linutronix.de Subject: Re: nohz and strange sleep latencies Message-ID: <20071119211142.GA1857@elf.ucw.cz> References: <20071119203152.GA1772@elf.ucw.cz> <20071119205555.GA28696@elte.hu> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20071119205555.GA28696@elte.hu> 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! > > On unloaded x60 system, 2.6.24-rc3 (tainted-pavel-so if someone can > > reproduce it, it would be helpful): > > > > pavel@amd:~$ while true; do time sleep 0.01; done > > 0.00user 0.00system 0.01 (0m0.013s) elapsed 30.71%CPU > > 0.00user 0.00system 0.02 (0m0.024s) elapsed 8.36%CPU > > 0.00user 0.00system 0.01 (0m0.013s) elapsed 15.53%CPU > > 0.00user 0.00system 0.02 (0m0.026s) elapsed 7.75%CPU > > 0.00user 0.00system 0.01 (0m0.013s) elapsed 23.34%CPU > > 0.00user 0.00system 0.20 (0m0.207s) elapsed 1.45%CPU > > 0.00user 0.00system 0.01 (0m0.013s) elapsed 15.59%CPU > > 0.00user 0.00system 0.23 (0m0.230s) elapsed 1.30%CPU > > 0.00user 0.00system 0.01 (0m0.013s) elapsed 15.61%CPU > > 0.00user 0.00system 0.20 (0m0.201s) elapsed 1.48%CPU > > 0.00user 0.00system 0.01 (0m0.013s) elapsed 15.50%CPU > > 0.00user 0.00system 0.19 (0m0.190s) elapsed 1.05%CPU > > 0.00user 0.00system 0.01 (0m0.013s) elapsed 23.37%CPU > > 0.00user 0.00system 0.04 (0m0.049s) elapsed 4.09%CPU > > 0.00user 0.00system 0.01 (0m0.013s) elapsed 23.35%CPU > > 0.00user 0.00system 0.01 (0m0.017s) elapsed 11.89%CPU > > 0.00user 0.00system 0.01 (0m0.013s) elapsed 23.38%CPU > > 0.00user 0.00system 0.08 (0m0.081s) elapsed 3.71%CPU > > 0.00user 0.00system 0.01 (0m0.013s) elapsed 23.33%CPU > > 0.00user 0.00system 0.01 (0m0.019s) elapsed 15.92%CPU > > > > nohz=off helps a lot. while true; do time sleep 0.0; done does not > > have unexpected latencies. > > does hpet=disable on the boot line also help? (without nohz=off) hpet-disable helps.. a bit. 200msec latencies are gone. (What is used for wakeups in this case?) pavel@amd:~$ while true; do time sleep 0.01; done 0.00user 0.00system 0.01 (0m0.013s) elapsed 22.96%CPU 0.00user 0.00system 0.01 (0m0.018s) elapsed 11.05%CPU 0.00user 0.00system 0.01 (0m0.013s) elapsed 15.54%CPU 0.00user 0.00system 0.03 (0m0.037s) elapsed 8.05%CPU 0.00user 0.00system 0.01 (0m0.013s) elapsed 23.34%CPU 0.00user 0.00system 0.03 (0m0.037s) elapsed 8.14%CPU 0.00user 0.00system 0.01 (0m0.013s) elapsed 23.33%CPU 0.00user 0.00system 0.03 (0m0.037s) elapsed 8.16%CPU 0.00user 0.00system 0.01 (0m0.013s) elapsed 23.30%CPU 0.00user 0.00system 0.03 (0m0.037s) elapsed 5.47%CPU 0.00user 0.00system 0.01 (0m0.013s) elapsed 23.25%CPU 0.00user 0.00system 0.01 (0m0.013s) elapsed 15.54%CPU 0.00user 0.00system 0.01 (0m0.013s) elapsed 15.56%CPU 0.00user 0.00system 0.03 (0m0.036s) elapsed 5.49%CPU 0.00user 0.00system 0.01 (0m0.013s) elapsed 23.35%CPU 0.00user 0.00system 0.03 (0m0.037s) elapsed 8.14%CPU 0.00user 0.00system 0.01 (0m0.013s) elapsed 23.35%CPU 0.00user 0.00system 0.03 (0m0.037s) elapsed 8.14%CPU 0.00user 0.00system 0.01 (0m0.013s) elapsed 23.34%CPU Pavel -- (english) http://www.livejournal.com/~pavelmachek (cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html