Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757793AbXK0Ege (ORCPT ); Mon, 26 Nov 2007 23:36:34 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1753143AbXK0Eg1 (ORCPT ); Mon, 26 Nov 2007 23:36:27 -0500 Received: from idcmail-mo1so.shaw.ca ([24.71.223.10]:56936 "EHLO pd3mo3so.prod.shaw.ca" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754237AbXK0Eg0 (ORCPT ); Mon, 26 Nov 2007 23:36:26 -0500 Date: Mon, 26 Nov 2007 22:36:17 -0600 From: Robert Hancock Subject: Re: Dynticks Causing High Context Switch Rate in ksoftirqd In-reply-to: To: bdupree@techfinesse.com Cc: linux-kernel@vger.kernel.org Message-id: <474B9EC1.5020304@shaw.ca> MIME-version: 1.0 Content-type: text/plain; charset=ISO-8859-1; format=flowed Content-transfer-encoding: 7bit References: User-Agent: Thunderbird 2.0.0.9 (Windows/20071031) Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1506 Lines: 36 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.. -- Robert Hancock Saskatoon, SK, Canada To email, remove "nospam" from hancockr@nospamshaw.ca Home Page: http://www.roberthancock.com/ - 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/