Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1758467AbXK0FjU (ORCPT ); Tue, 27 Nov 2007 00:39:20 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1751314AbXK0FjI (ORCPT ); Tue, 27 Nov 2007 00:39:08 -0500 Received: from pentafluge.infradead.org ([213.146.154.40]:45041 "EHLO pentafluge.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751431AbXK0FjG (ORCPT ); Tue, 27 Nov 2007 00:39:06 -0500 Date: Mon, 26 Nov 2007 21:38:47 -0800 From: Arjan van de Ven To: Robert Hancock Cc: bdupree@techfinesse.com, linux-kernel@vger.kernel.org Subject: Re: Dynticks Causing High Context Switch Rate in ksoftirqd Message-ID: <20071126213847.4768b1f2@laptopd505.fenrus.org> In-Reply-To: <474B9EC1.5020304@shaw.ca> References: <474B9EC1.5020304@shaw.ca> Organization: Intel X-Mailer: Claws Mail 3.0.2 (GTK+ 2.12.1; i386-redhat-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit X-SRS-Rewrite: SMTP reverse-path rewritten from by pentafluge.infradead.org See http://www.infradead.org/rpr.html Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1765 Lines: 44 On Mon, 26 Nov 2007 22:36:17 -0600 Robert Hancock wrote: > bdupree@techfinesse.com wrote: > > Question: Why is ksoftirqd eating about 5 to 10 percent of my CPU > > on an idle system? The problem occurs if I config the kernel with > > tickless support (i.e. CONFIG_TICK_ONESHOT=y). (Thanks to > > "oprofile" for putting me onto this.) > > > > I have noted this same problem on kernel versions: 2.6.23.1, > > 2.6.23.8 and 2.6.23.9 > > > > ************************************************************************** > > *** Output from "vmstat -n 1 10" -- Note very high context switch > > rate *** *** This is on a idle > > machine! *** > > ************************************************************************** > > > > procs -----------memory---------- ---swap-- -----io---- --system-- > > ----cpu---- > > r b swpd free buff cache si so bi bo in cs > > us sy id wa > > 0 0 0 1925556 4768 116104 0 0 124 2 6 > > 7538 1 2 96 1 > > 0 0 0 1925556 4768 116104 0 0 0 0 2 > > 147329 0 1 99 0 > > What did oprofile show? It should be able to narrow down what > function(s) are responsible for the CPU usage.. > or better, what does powertop version 1.9 show? that tends to show tickless wakeup artifacts quite nicely -- If you want to reach me at my work email, use arjan@linux.intel.com For development, discussion and tips for power savings, visit http://www.lesswatts.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/