From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752158AbXKSUfZ (ORCPT ); Mon, 19 Nov 2007 15:35:25 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1751163AbXKSUfP (ORCPT ); Mon, 19 Nov 2007 15:35:15 -0500 Received: from gprs189-60.eurotel.cz ([160.218.189.60]:37855 "EHLO amd.ucw.cz" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1751099AbXKSUfO (ORCPT ); Mon, 19 Nov 2007 15:35:14 -0500 Date: Mon, 19 Nov 2007 21:31:52 +0100 From: Pavel Machek To: kernel list , Ingo Molnar , tglx@linutronix.de Subject: nohz and strange sleep latencies Message-ID: <20071119203152.GA1772@elf.ucw.cz> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline 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. Pavel -- (english) http://www.livejournal.com/~pavelmachek (cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html