From owner-freebsd-hackers@FreeBSD.ORG Sat Sep 28 10:38:06 2013 Return-Path: Delivered-To: freebsd-hackers@freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [8.8.178.115]) (using TLSv1 with cipher ADH-AES256-SHA (256/256 bits)) (No client certificate requested) by hub.freebsd.org (Postfix) with ESMTP id 6F094C97 for ; Sat, 28 Sep 2013 10:38:06 +0000 (UTC) (envelope-from peter@rulingia.com) Received: from vps.rulingia.com (host-122-100-2-194.octopus.com.au [122.100.2.194]) (using TLSv1 with cipher DHE-RSA-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.freebsd.org (Postfix) with ESMTPS id 06E2C2359 for ; Sat, 28 Sep 2013 10:38:05 +0000 (UTC) Received: from server.rulingia.com (c220-239-237-213.belrs5.nsw.optusnet.com.au [220.239.237.213]) by vps.rulingia.com (8.14.7/8.14.5) with ESMTP id r8SAc3cV025181 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-SHA bits=256 verify=OK) for ; Sat, 28 Sep 2013 20:38:04 +1000 (EST) (envelope-from peter@rulingia.com) X-Bogosity: Ham, spamicity=0.000000 Received: from server.rulingia.com (localhost.rulingia.com [127.0.0.1]) by server.rulingia.com (8.14.7/8.14.7) with ESMTP id r8SAbwWn027857 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-GCM-SHA384 bits=256 verify=NO) for ; Sat, 28 Sep 2013 20:37:58 +1000 (EST) (envelope-from peter@server.rulingia.com) Received: (from peter@localhost) by server.rulingia.com (8.14.7/8.14.7/Submit) id r8SAbwWI027856 for freebsd-hackers@freebsd.org; Sat, 28 Sep 2013 20:37:58 +1000 (EST) (envelope-from peter) Date: Sat, 28 Sep 2013 20:37:58 +1000 From: Peter Jeremy To: freebsd-hackers@freebsd.org Subject: Mixing amd64 kernel with i386 world Message-ID: <20130928103758.GC27231@server.rulingia.com> MIME-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha1; protocol="application/pgp-signature"; boundary="k1lZvvs/B4yU6o8G" Content-Disposition: inline X-PGP-Key: http://www.rulingia.com/keys/peter.pgp User-Agent: Mutt/1.5.21 (2010-09-15) 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 10:38:06 -0000 --k1lZvvs/B4yU6o8G Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Content-Transfer-Encoding: quoted-printable 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? --=20 Peter Jeremy --k1lZvvs/B4yU6o8G Content-Type: application/pgp-signature -----BEGIN PGP SIGNATURE----- Version: GnuPG v2.0.21 (FreeBSD) iEYEARECAAYFAlJGsYYACgkQ/opHv/APuIckqQCgxMZcBfolKIOglm0jy7JeJS+D sAIAoK0+PtR5Bn+uKZmbS2ZeSkZNpTEj =jH8y -----END PGP SIGNATURE----- --k1lZvvs/B4yU6o8G--