From owner-freebsd-hackers@FreeBSD.ORG Wed Aug 26 20:43:54 2009 Return-Path: Delivered-To: freebsd-hackers@freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:4f8:fff6::34]) by hub.freebsd.org (Postfix) with ESMTP id 888BF106568B for ; Wed, 26 Aug 2009 20:43:54 +0000 (UTC) (envelope-from jhb@freebsd.org) Received: from cyrus.watson.org (cyrus.watson.org [65.122.17.42]) by mx1.freebsd.org (Postfix) with ESMTP id 59F0B8FC25 for ; Wed, 26 Aug 2009 20:43:54 +0000 (UTC) Received: from bigwig.baldwin.cx (66.111.2.69.static.nyinternet.net [66.111.2.69]) by cyrus.watson.org (Postfix) with ESMTPSA id ED01E46B58; Wed, 26 Aug 2009 16:43:53 -0400 (EDT) Received: from jhbbsd.hudson-trading.com (unknown [209.249.190.8]) by bigwig.baldwin.cx (Postfix) with ESMTPA id 495C68A02A; Wed, 26 Aug 2009 16:43:53 -0400 (EDT) From: John Baldwin To: freebsd-hackers@freebsd.org Date: Wed, 26 Aug 2009 16:42:59 -0400 User-Agent: KMail/1.9.7 References: <237c27100908261203g7e771400o2d9603220d1f1e0b@mail.gmail.com> In-Reply-To: <237c27100908261203g7e771400o2d9603220d1f1e0b@mail.gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: 7bit Content-Disposition: inline Message-Id: <200908261642.59419.jhb@freebsd.org> X-Greylist: Sender succeeded SMTP AUTH, not delayed by milter-greylist-4.0.1 (bigwig.baldwin.cx); Wed, 26 Aug 2009 16:43:53 -0400 (EDT) X-Virus-Scanned: clamav-milter 0.95.1 at bigwig.baldwin.cx X-Virus-Status: Clean X-Spam-Status: No, score=-2.5 required=4.2 tests=AWL,BAYES_00,RDNS_NONE autolearn=no version=3.2.5 X-Spam-Checker-Version: SpamAssassin 3.2.5 (2008-06-10) on bigwig.baldwin.cx Cc: Linda Messerschmidt Subject: Re: Intermittent system hangs on 7.2-RELEASE-p1 X-BeenThere: freebsd-hackers@freebsd.org X-Mailman-Version: 2.1.5 Precedence: list List-Id: Technical Discussions relating to FreeBSD List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Wed, 26 Aug 2009 20:43:54 -0000 On Wednesday 26 August 2009 3:03:13 pm Linda Messerschmidt wrote: > I'm trying to troubleshoot an intermittent Apache performance problem, > and I've narrowed it down using to what appears to be a brief > whole-system hang that last from 0.5 - 3 seconds. They occur every > few minutes. One thing to note is that ktrace only logs voluntary context switches (i.e. call to tsleep or waiting on a condition variable). It specifically does not log preemptions or blocking on a mutex, so in theory if your machine was livelocked temporarily that might explain this. -- John Baldwin