From owner-freebsd-stable@FreeBSD.ORG Tue May 29 21:12:52 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 19310106566B for ; Tue, 29 May 2012 21:12:52 +0000 (UTC) (envelope-from kjkoster@gmail.com) Received: from mail-wg0-f50.google.com (mail-wg0-f50.google.com [74.125.82.50]) by mx1.freebsd.org (Postfix) with ESMTP id 99A468FC12 for ; Tue, 29 May 2012 21:12:51 +0000 (UTC) Received: by wgbds11 with SMTP id ds11so4341809wgb.31 for ; Tue, 29 May 2012 14:12:50 -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=bKtkqcuNMlAYWvmjrerrHIt4aiV0u9MrQLmGHWibSdE=; b=ipbYGy4VKCvbm1BjoMK+lh5i6kpNU+ohKI1vVHgYVF2vOUSFIHHAjue4uIo042XOrx zG/KHFTXc5I2SGJdN3UIECK4Fx+ddF21PE+TsIJdR4OIw75aR2oQZinQPJ7ltpF1dNaG BR7TnqYU8k70MCuBvH9ZFIDGEHsEuksdwZrisnL5JHDIfngvmNnBPwozuR2xFn/xdXzE UEIRmnj7H4f9qp8Jme+1YCDwO4QtZ3yKDtLZLl5kGumdaakF7vmYvxtonjLeFKO2leTg 1ZkX5gqmuaMRJYAEBm7hzdKO+oPfKEr24rCv12YpIJk9PZ8OZQ6I6pypaPt1U+mMrLsn Fyiw== Received: by 10.216.211.131 with SMTP id w3mr8185567weo.163.1338325970677; Tue, 29 May 2012 14:12:50 -0700 (PDT) Received: from kees-jan-kosters-macbook-air.fritz.box (kjkoster.org. [83.163.197.206]) by mx.google.com with ESMTPS id q6sm31208273wiy.0.2012.05.29.14.12.48 (version=TLSv1/SSLv3 cipher=OTHER); Tue, 29 May 2012 14:12:49 -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 23:12:47 +0200 Content-Transfer-Encoding: quoted-printable Message-Id: <17320979-2ED2-4DF2-97E9-09035F4DD3BB@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 21:12:52 -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 I looked at "sysctl kern.geom.confdot" (another ridiculously useful = feature) to see where the scheduler should be placed. The way I was thinking, I should place a scheduler in such a way that = writes to one physical device (ada3 in my case) do not cause reads on = another device to stall (e.g. ada2, where the database lives). However, = it looks like the GEOM tree is actually a GEOM bush, with a separate = tree for each device. Am I missing something? Is there a way to schedule across devices? Is = the bush a tree after all, maybe? -- Kees Jan http://java-monitor.com/ kjkoster@kjkoster.org +31651838192 The secret of success lies in the stability of the goal. -- Benjamin = Disraeli