From owner-freebsd-hackers@FreeBSD.ORG Mon Sep 14 13:28:26 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 0DA481065670 for ; Mon, 14 Sep 2009 13:28:26 +0000 (UTC) (envelope-from ghelmer@palisadesys.com) Received: from cetus.palisadesys.com (cetus.palisadesys.isupark.org [205.237.115.21]) by mx1.freebsd.org (Postfix) with ESMTP id 9190D8FC21 for ; Mon, 14 Sep 2009 13:28:25 +0000 (UTC) Received: from cancer.palisadesys.com (serverwatch [172.16.1.98]) by cetus.palisadesys.com (8.14.3/8.14.3) with ESMTP id n8EDF9IW017699; Mon, 14 Sep 2009 08:15:09 -0500 (CDT) (envelope-from ghelmer@palisadesys.com) Received: from GuysMBP.local (cetus.palisadesys.isupark.org [205.237.115.21]) (authenticated bits=0) by cancer.palisadesys.com (8.14.2/8.14.2) with ESMTP id n8EDF7mo003404 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-SHA bits=256 verify=NO); Mon, 14 Sep 2009 08:15:07 -0500 (CDT) (envelope-from ghelmer@palisadesys.com) Message-ID: <4AAE41DB.9050104@palisadesys.com> Date: Mon, 14 Sep 2009 08:15:07 -0500 From: Guy Helmer User-Agent: Thunderbird 2.0.0.23 (Macintosh/20090812) MIME-Version: 1.0 To: Linda Messerschmidt References: <237c27100908261203g7e771400o2d9603220d1f1e0b@mail.gmail.com> <200909111102.14503.jhb@freebsd.org> <237c27100909111035y544e8c91hc7726fd6ef16e351@mail.gmail.com> <200909111506.47309.jhb@freebsd.org> <237c27100909111905y244924c1n93b4e4d9ceda44be@mail.gmail.com> <237c27100909112055i35612b4btbfbecb8b5dd1568c@mail.gmail.com> <4AAB1E34.2060908@elischer.org> <237c27100909112147h64f71585p2a97f2b48a510985@mail.gmail.com> In-Reply-To: <237c27100909112147h64f71585p2a97f2b48a510985@mail.gmail.com> Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit X-Greylist: Sender succeeded SMTP AUTH authentication, not delayed by milter-greylist-3.0 (cancer.palisadesys.com [205.237.115.20]); Mon, 14 Sep 2009 08:15:07 -0500 (CDT) X-Palisade-MailScanner-Information: Please contact the ISP for more information X-Palisade-MailScanner: Found to be clean X-Palisade-MailScanner-SpamCheck: not spam (whitelisted), SpamAssassin (not cached, score=-4.399, required 6, autolearn=not spam, ALL_TRUSTED -1.80, BAYES_00 -2.60) X-Palisade-MailScanner-From: ghelmer@palisadesys.com Cc: freebsd-hackers@freebsd.org 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: Mon, 14 Sep 2009 13:28:26 -0000 Linda Messerschmidt wrote: > Well, this is interesting. I got really frustrated with the other > approach, so I thought I'd thin a machine down absolutely as far as I > could, eliminate every possible source of delay, and see what happens. > I killed everything... cron, RPC, NFS, devd, gmon, nrpe, everything. > The Apache and its exerciser are now the only things running on the > machine, and the Apache is only touching an md0 swap device mounted on > /mnt. I *still* get the hangs. > > It hangs for all sorts of different periods, but the duration of the > stall is approximately inversely proportional to the chance of seeing > it. To get a short delay, you need wait only a little bit. If you > want a 2-3 second delay, you may have to wait 15-20 minutes. > On what sort of hardware is this hang occurring? Several months ago I was trying to resolve an intermittent hang under FreeBSD 7. I collected a large number of crashdumps I created using the kernel debugger when I caught the machine hanging, but the backtraces were very inconsistent, and the hang was only occurring on Xeons with multithreading (older 2.8GHz and 3.6GHz Xeons). I was able to prevent the hang by setting "mach.hyperthreading_enabled=0" in /boot/loader.conf, but I am still not sure why it worked. Guy