From owner-freebsd-stable@FreeBSD.ORG Mon Dec 1 22:41:34 2008 Return-Path: Delivered-To: freebsd-stable@freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:4f8:fff6::34]) by hub.freebsd.org (Postfix) with ESMTP id 665A91065676 for ; Mon, 1 Dec 2008 22:41:33 +0000 (UTC) (envelope-from janm@transactionware.com) Received: from mail.transactionware.com (mail.transactionware.com [203.14.245.7]) by mx1.freebsd.org (Postfix) with SMTP id A80148FC12 for ; Mon, 1 Dec 2008 22:41:32 +0000 (UTC) (envelope-from janm@transactionware.com) Received: (qmail 54054 invoked from network); 1 Dec 2008 22:41:52 -0000 Received: from midgard.transactionware.com (192.168.1.55) by dm.transactionware.com with SMTP; 1 Dec 2008 22:41:52 -0000 Received: (qmail 14228 invoked by uid 907); 1 Dec 2008 22:41:30 -0000 Received: from midgard.transactionware.com (HELO STUDYPC) (192.168.1.55) by midgard.transactionware.com (qpsmtpd/0.40) with ESMTP; Tue, 02 Dec 2008 09:41:30 +1100 From: "Jan Mikkelsen" To: , "'FreeBSD Stable'" Date: Tue, 2 Dec 2008 09:41:22 +1100 Message-ID: <1A7634CAC3E147CB8B5CDA853E4856D7@STUDYPC> MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: quoted-printable X-Priority: 3 (Normal) X-MSMail-Priority: Normal X-Mailer: Microsoft Outlook, Build 10.0.6838 Importance: Normal Thread-Index: AclUBe9HTTQHEcgLQ5WPl5twJaurjA== X-MimeOLE: Produced By Microsoft MimeOLE V6.00.2900.5579 Cc: Subject: Re: no priority on the console? X-BeenThere: freebsd-stable@freebsd.org X-Mailman-Version: 2.1.5 Precedence: list List-Id: Production branch of FreeBSD source code List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Mon, 01 Dec 2008 22:41:34 -0000 Hi, > As per my previous message, I've spent about 3 months trying to debug = > a problem that was causing all disk I/O to go very slowly. A first glance this sounds similar to the problem I am having with very = slow I/O on the Areca controller. (see: "7.1-PRERELEASE: arcmsr write performance problem") What controller are you using? Is the write = cache enabled? > One of the things which made this nearly impossible to diagnose was =20 > the absolute lack of priority given to the console. Logging in on the = =20 > console would take 12-15 minutes. Hitting enter on the console would = > usually take between 3 and 5 minutes. Yes, I see this when I get the slow I/O problem. I think this has been = a problem for some time; I have also seen "console freezes" (ssh, console, etc.) on 6.0 and 6.1 systems under SATA load. That was a while ago now (2006?). I also recall others reporting have seen the same problem intermittently. > This doesn't seem right to me. Can someone explain why the console =20 > isn't given a very high priority? Why not? What other mechanism does = =20 > the sysadmin have for debugging, at a time when SSH logins either =20 > fail, or take up to an hour to complete? In my case I could log into the system and start things like iostat and gstat and they kept running while the problem occurred so that I could = see some of what was going on. I could also have what seemed like a = reasonable ssh session with a jail on the same machine. This indicates to me that = it is not the console that is the issue, but rather that the process of = logging into the main machine touches some file that causes it to get caught up = in the slow I/O quagmire. If the problem I am seeing now is the same as the one I saw a few years = ago then I think the nature might have changed. My recollection is that utilities like iostat would also freeze back then, but I can't be sure. I'd like to resolve this problem too. Regards, Jan.