From owner-freebsd-stable@FreeBSD.ORG Tue May 29 20:54:57 2012 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 5DDE01065686 for ; Tue, 29 May 2012 20:54:57 +0000 (UTC) (envelope-from kjkoster@gmail.com) Received: from mail-wi0-f178.google.com (mail-wi0-f178.google.com [209.85.212.178]) by mx1.freebsd.org (Postfix) with ESMTP id D7C888FC17 for ; Tue, 29 May 2012 20:54:56 +0000 (UTC) Received: by wibhn6 with SMTP id hn6so2523368wib.13 for ; Tue, 29 May 2012 13:54:50 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20120113; h=subject:mime-version:content-type:from:in-reply-to:date:cc :content-transfer-encoding:message-id:references:to:x-mailer; bh=1Qn4kPW5NjUvE0axycQvdJuDK6i+3uJnF3zkGI13sCU=; b=MU5fIBNTPRm8Hbse7jf/b6OQbF9eaVcbmn5bIjz5fbBH+9hplezFj03qiG30ZSauvV ZbeTqeu2DCrkEt2PfUg2D2Sbz5yV/sQB2Ok+7oT1MOGjXz10LTcUGMQ9CwvrT6Dgo7o0 rZuawnjUMFfxS8fIaLqUNZjPfkbg/WzRdIrV454giN3CGS8gGxPltllOZasOpNiWmEBM kFdIBlWZ9PPdHgrQqBNNWcFm+mp0x5kUpkCV7fp1VFZq7ECy4ArZ80QJDnOn+gvKhlDv 7Onx99xGjfpdgfZ/JNEOm/ecaCjA1mUksu1KXNw9WQeMJYz43JKZB6ZMP+RWTUu4tCh9 uH5Q== Received: by 10.216.140.160 with SMTP id e32mr8940466wej.46.1338324888079; Tue, 29 May 2012 13:54:48 -0700 (PDT) Received: from kees-jan-kosters-macbook-air.fritz.box (kjkoster.org. [83.163.197.206]) by mx.google.com with ESMTPS id gv4sm48531692wib.8.2012.05.29.13.54.47 (version=TLSv1/SSLv3 cipher=OTHER); Tue, 29 May 2012 13:54:47 -0700 (PDT) Mime-Version: 1.0 (Apple Message framework v1278) Content-Type: text/plain; charset=us-ascii From: Kees Jan Koster In-Reply-To: Date: Tue, 29 May 2012 22:54:43 +0200 Content-Transfer-Encoding: quoted-printable Message-Id: <0B516D83-3CFA-4263-8052-90CF579E7FA8@gmail.com> References: To: Freddie Cash X-Mailer: Apple Mail (2.1278) Cc: freebsd-stable@freebsd.org Subject: Re: FreeBSD 9.0 hangs on heavy I/O 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: Tue, 29 May 2012 20:54:57 -0000 Dear Freddie, >> You may want to play around with gshed, the GEOM Scheduler. >>=20 >> Matt Dillon did a bunch of tests comparing FreeBSD+UFS to >> DragonflyBSD+HAMMER and found that FreeBSD starves read threads in >> order to satisfy write threads (or the other way around?). But, >> adding gsched into the mix helped things immensely, allowing mixed >> reads/writes to better shares disk I/O resources. >>=20 >> I'll see if I can dig up a link to his testing e-mail messages. >=20 > Here's the post, part of a thread on benchmarking RAID controllers: >=20 > http://leaf.dragonflybsd.org/mailarchive/kernel/2011-07/msg00034.html *cloink* /me goes to pick my jam off of the floor. I can insert a I/O = scheduler in full flight? Ok. I need to adjust my mental image of the = world a bit. I just played with the examples on a test machine and the effect is = quite visible. I ran a CVS checkout of the ports collection concurrent = with dd writing a massive file. Insert scheduler -> CVS update is = faster; destroy scheduler -> CVS update crawls. This is so easy it's = almost scary. The behaviour that Matt describes is what I thought I was seeing too: = write a *lot* and it becomes hard to read from the disk. In my system, = writing data is largely asynchronous and can lag the actual arrival of = data by as much as a few minutes. Reads are always synchronous to a user = request and need to be served asap. Some writes are database writes and = they should be services quickly too. This is definitively something I need to look into. Thank you for the = reference. -- Kees Jan http://java-monitor.com/ kjkoster@kjkoster.org +31651838192 Change is good. Granted, it is good in retrospect, but change is good.