From owner-freebsd-hackers@FreeBSD.ORG Sat Sep 28 13:56:46 2013 Return-Path: Delivered-To: freebsd-hackers@FreeBSD.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:1900:2254:206a::19:1]) (using TLSv1 with cipher ADH-AES256-SHA (256/256 bits)) (No client certificate requested) by hub.freebsd.org (Postfix) with ESMTP id 0A7D5574 for ; Sat, 28 Sep 2013 13:56:46 +0000 (UTC) (envelope-from ian@FreeBSD.org) Received: from mho-02-ewr.mailhop.org (mho-02-ewr.mailhop.org [204.13.248.72]) (using TLSv1 with cipher DHE-RSA-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.freebsd.org (Postfix) with ESMTPS id D59BE2D81 for ; Sat, 28 Sep 2013 13:56:45 +0000 (UTC) Received: from c-24-8-230-52.hsd1.co.comcast.net ([24.8.230.52] helo=damnhippie.dyndns.org) by mho-02-ewr.mailhop.org with esmtpsa (TLSv1:AES256-SHA:256) (Exim 4.72) (envelope-from ) id 1VPv0h-000Lmi-By; Sat, 28 Sep 2013 13:56:39 +0000 Received: from [172.22.42.240] (revolution.hippie.lan [172.22.42.240]) by damnhippie.dyndns.org (8.14.3/8.14.3) with ESMTP id r8SDuZx8007744; Sat, 28 Sep 2013 07:56:36 -0600 (MDT) (envelope-from ian@FreeBSD.org) X-Mail-Handler: Dyn Standard SMTP by Dyn X-Originating-IP: 24.8.230.52 X-Report-Abuse-To: abuse@dyndns.com (see http://www.dyndns.com/services/sendlabs/outbound_abuse.html for abuse reporting information) X-MHO-User: U2FsdGVkX18PMtJ6pl9pbI6a/EJXWyiv Subject: Re: Mixing amd64 kernel with i386 world From: Ian Lepore To: Peter Jeremy In-Reply-To: <20130928103758.GC27231@server.rulingia.com> References: <20130928103758.GC27231@server.rulingia.com> Content-Type: text/plain; charset="us-ascii" Date: Sat, 28 Sep 2013 07:56:35 -0600 Message-ID: <1380376595.1197.309.camel@revolution.hippie.lan> Mime-Version: 1.0 X-Mailer: Evolution 2.32.1 FreeBSD GNOME Team Port Content-Transfer-Encoding: 7bit Cc: freebsd-hackers@FreeBSD.org X-BeenThere: freebsd-hackers@freebsd.org X-Mailman-Version: 2.1.14 Precedence: list List-Id: Technical Discussions relating to FreeBSD List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Sat, 28 Sep 2013 13:56:46 -0000 On Sat, 2013-09-28 at 20:37 +1000, Peter Jeremy wrote: > I have a system with 4GB RAM and hence need to use an amd64 kernel to use > all the RAM (I can only access 3GB RAM with an i386 kernel). OTOH, amd64 > processes are significantly (50-100%) larger than equivalent i386 processes > and none none of the applications I'll be running on the system need to be > 64-bit. > > This implies that the optimal approach is an amd64 kernel with i386 > userland (I'm ignoring PAE as a useable approach). I've successfully > run i386 jails on amd64 systems so I know this mostly works. I also > know that there are some gotchas: > - kdump needs to match the kernel > - anything accessing /dev/mem or /dev/kmem (which implies anything that > uses libkvm) probably needs to match the kernel. > > Has anyone investigated this approach? > Why are you ignoring PAE? It's been working for me for years. -- Ian