From owner-freebsd-fs@FreeBSD.ORG Wed Jun 10 01:22:42 2009 Return-Path: Delivered-To: freebsd-fs@freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:4f8:fff6::34]) by hub.freebsd.org (Postfix) with ESMTP id 9F5AA106566C for ; Wed, 10 Jun 2009 01:22:42 +0000 (UTC) (envelope-from mat.macy@gmail.com) Received: from an-out-0708.google.com (an-out-0708.google.com [209.85.132.245]) by mx1.freebsd.org (Postfix) with ESMTP id 553698FC1C for ; Wed, 10 Jun 2009 01:22:41 +0000 (UTC) (envelope-from mat.macy@gmail.com) Received: by an-out-0708.google.com with SMTP id c3so214658ana.13 for ; Tue, 09 Jun 2009 18:22:41 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=gamma; h=domainkey-signature:mime-version:sender:received:date :x-google-sender-auth:message-id:subject:from:to:content-type :content-transfer-encoding; bh=qllLNVpZX4AXQNw3rRxecRPZL3k0jqyNbTaJ4w0kWAs=; b=LKzYW+V9AMQhRT4AAKP8N4QOepovF41tIUs+V5vOe1S3au0mhhPLfm2a+cY64XV8GQ lM9dWt7PVyRGmYXuX0rAb1DXinwaK1vIeXqT9R2iKvpsU3Jkq4Jd1c0Uqot+hb/HR8Uf 76jVg011HdMxXfpk5hGJXD8IPcvFizALvxW/c= DomainKey-Signature: a=rsa-sha1; c=nofws; d=gmail.com; s=gamma; h=mime-version:sender:date:x-google-sender-auth:message-id:subject :from:to:content-type:content-transfer-encoding; b=d3R6AmFUwIXlhjXqy+0FE9WBGoJI54VBRa7UlZLbEVwzWzoIQnkSYpppbqhdKGjvDn 6W54StoYjuLF95w7kpym65LkkKrwVKrDQ4nhnF3fcwUaat48w252DqOgwjIQfN8M/04N pTNlHkiZfvSIZb5lYoV+T9WgnfiYxQCmbXzpY= MIME-Version: 1.0 Sender: mat.macy@gmail.com Received: by 10.100.153.12 with SMTP id a12mr745356ane.159.1244596960976; Tue, 09 Jun 2009 18:22:40 -0700 (PDT) Date: Tue, 9 Jun 2009 18:22:40 -0700 X-Google-Sender-Auth: 5af4fae6fb9fc513 Message-ID: <3c1674c90906091822x56be5f2bg5b6156618847cc21@mail.gmail.com> From: Kip Macy To: freebsd-fs@freebsd.org Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Subject: heads up on prefetch tunable in ZFS X-BeenThere: freebsd-fs@freebsd.org X-Mailman-Version: 2.1.5 Precedence: list List-Id: Filesystems List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Wed, 10 Jun 2009 01:22:42 -0000 As far as I can tell systems that have less than 4GB are more often hurt by prefetched than helped. On i386 systems and systems with less than 4GB, as of 193878 prefetch is now disabled by default. I've added a prefetch enable tunable, to enable prefetching for those systems. The prefetch disable tunable will continue to unconditionally disable prefetching. Cheers, Kip