Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755901AbXK1F2k (ORCPT ); Wed, 28 Nov 2007 00:28:40 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1750898AbXK1F2a (ORCPT ); Wed, 28 Nov 2007 00:28:30 -0500 Received: from smtp2.linux-foundation.org ([207.189.120.14]:39775 "EHLO smtp2.linux-foundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750805AbXK1F23 (ORCPT ); Wed, 28 Nov 2007 00:28:29 -0500 Date: Tue, 27 Nov 2007 21:28:05 -0800 From: Andrew Morton To: Robert Hancock Cc: bdupree@techfinesse.com, linux-kernel@vger.kernel.org Subject: Re: Dynticks Causing High Context Switch Rate in ksoftirqd Message-Id: <20071127212805.31f0de96.akpm@linux-foundation.org> In-Reply-To: <474B9EC1.5020304@shaw.ca> References: <474B9EC1.5020304@shaw.ca> X-Mailer: Sylpheed 2.4.1 (GTK+ 2.8.17; x86_64-unknown-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1838 Lines: 48 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.. Sigh. I just asked a similar thing. Let's look at the mail headers: Message-ID: <41877.67.173.156.207.1196130992.squirrel@www.techfinesse.net> ... From: bdupree@techfinesse.com From: Robert Hancock ... In-reply-to: Please fix your email client so as to not break threading? - 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/