From owner-freebsd-stable@FreeBSD.ORG Tue Aug 5 17:01:39 2008 Return-Path: Delivered-To: stable@freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:4f8:fff6::34]) by hub.freebsd.org (Postfix) with ESMTP id C1752106564A for ; Tue, 5 Aug 2008 17:01:39 +0000 (UTC) (envelope-from cswiger@mac.com) Received: from mail-out4.apple.com (mail-out4.apple.com [17.254.13.23]) by mx1.freebsd.org (Postfix) with ESMTP id A88918FC08 for ; Tue, 5 Aug 2008 17:01:39 +0000 (UTC) (envelope-from cswiger@mac.com) Received: from relay12.apple.com (relay12.apple.com [17.128.113.53]) by mail-out4.apple.com (Postfix) with ESMTP id 3D8AC36F8A24; Tue, 5 Aug 2008 09:46:20 -0700 (PDT) Received: from relay12.apple.com (unknown [127.0.0.1]) by relay12.apple.com (Symantec Mail Security) with ESMTP id 25116464006; Tue, 5 Aug 2008 09:46:20 -0700 (PDT) X-AuditID: 11807135-a7df5bb000001321-88-489883dc5283 Received: from cswiger1.apple.com (cswiger1.apple.com [17.227.140.124]) (using TLSv1 with cipher AES128-SHA (128/128 bits)) (No client certificate requested) by relay12.apple.com (Apple SCV relay) with ESMTP id 0E8FE420004; Tue, 5 Aug 2008 09:46:20 -0700 (PDT) Message-Id: From: Chuck Swiger To: Lin Jui-Nan Eric In-Reply-To: <47713ee10808050839k5b258831x66bc52f70b2c355b@mail.gmail.com> Content-Type: text/plain; charset=US-ASCII; format=flowed; delsp=yes Content-Transfer-Encoding: 7bit Mime-Version: 1.0 (Apple Message framework v928.1) Date: Tue, 5 Aug 2008 09:46:19 -0700 References: <47713ee10808050839k5b258831x66bc52f70b2c355b@mail.gmail.com> X-Mailer: Apple Mail (2.928.1) X-Brightmail-Tracker: AAAAAA== Cc: stable@freebsd.org Subject: Re: Max size of one swap slice 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, 05 Aug 2008 17:01:39 -0000 On Aug 5, 2008, at 8:39 AM, Lin Jui-Nan Eric wrote: > Recently we found that we can only allocate 32GB for one swap slice. > Does there is any sysctl oid or any kernel option to increase it? Why > we have this restriction? This size limitation likely predates the availability of disks larger than 32GB. It's hard to conceive of why you'd want to add so much swap space, anyway-- if you've got programs which actually need to deal with 10s of gigabytes worth of data, then they ought to maintain a smaller/ reasonable-sized working set in RAM and do disk I/O as needed themselves rather than depend upon the VM pager, anyways. (Well, when using a BSD-derived kernel, anyways. Some of the Mach kernels support userland VM pager implementations, so that things like a database or Photoshop can provide their own pager which understands their workload and chooses which pages to evict or replace better than the default system pager algorithm can.) Regards, -- -Chuck