From owner-freebsd-current@FreeBSD.ORG  Sat Aug 16 23:26:59 2008
Return-Path: <owner-freebsd-current@FreeBSD.ORG>
Delivered-To: current@FreeBSD.ORG
Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:4f8:fff6::34])
	by hub.freebsd.org (Postfix) with ESMTP id BA5C4106564A
	for <current@FreeBSD.ORG>; Sat, 16 Aug 2008 23:26:59 +0000 (UTC)
	(envelope-from das@FreeBSD.ORG)
Received: from zim.MIT.EDU (ZIM.MIT.EDU [18.95.3.101])
	by mx1.freebsd.org (Postfix) with ESMTP id 6BE108FC16
	for <current@FreeBSD.ORG>; Sat, 16 Aug 2008 23:26:59 +0000 (UTC)
	(envelope-from das@FreeBSD.ORG)
Received: from zim.MIT.EDU (localhost [127.0.0.1])
	by zim.MIT.EDU (8.14.2/8.14.2) with ESMTP id m7GMrVhl094064;
	Sat, 16 Aug 2008 18:53:31 -0400 (EDT) (envelope-from das@FreeBSD.ORG)
Received: (from das@localhost)
	by zim.MIT.EDU (8.14.2/8.14.2/Submit) id m7GMrVrL094063;
	Sat, 16 Aug 2008 18:53:31 -0400 (EDT) (envelope-from das@FreeBSD.ORG)
Date: Sat, 16 Aug 2008 18:53:31 -0400
From: David Schultz <das@FreeBSD.ORG>
To: Barney Cordoba <barney_cordoba@yahoo.com>
Message-ID: <20080816225331.GA93918@zim.MIT.EDU>
Mail-Followup-To: Barney Cordoba <barney_cordoba@yahoo.com>,
	current@FreeBSD.ORG
References: <976425.95447.qm@web63901.mail.re1.yahoo.com>
Mime-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
In-Reply-To: <976425.95447.qm@web63901.mail.re1.yahoo.com>
Cc: current@FreeBSD.ORG
Subject: Re: Max Kernel Memory?
X-BeenThere: freebsd-current@freebsd.org
X-Mailman-Version: 2.1.5
Precedence: list
List-Id: Discussions about the use of FreeBSD-current
	<freebsd-current.freebsd.org>
List-Unsubscribe: <http://lists.freebsd.org/mailman/listinfo/freebsd-current>, 
	<mailto:freebsd-current-request@freebsd.org?subject=unsubscribe>
List-Archive: <http://lists.freebsd.org/pipermail/freebsd-current>
List-Post: <mailto:freebsd-current@freebsd.org>
List-Help: <mailto:freebsd-current-request@freebsd.org?subject=help>
List-Subscribe: <http://lists.freebsd.org/mailman/listinfo/freebsd-current>,
	<mailto:freebsd-current-request@freebsd.org?subject=subscribe>
X-List-Received-Date: Sat, 16 Aug 2008 23:26:59 -0000

On Fri, Aug 15, 2008, Barney Cordoba wrote:
> Setting vm.kmem_size to what seem to be usable values causes all kinds of memory allocations on boot. For example setting it to 1GB with 2GB installed results in a failure. 
> 
> What is the maximum amount of memory that can be allocated to the kernel, and why can't 1/2 of the system's memory be allocated safely? We have a module with a potentially very large dynamic lookup table, with little going on in userland, so we want to allocate as much as possible to the kernel.

As I recall, you also need to tweak KVA_PAGES on i386. The kernel
map can't be bigger than the total amount of address space alotted
to the kernel.