From owner-freebsd-hackers@FreeBSD.ORG Sun Sep 29 08:29:11 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 651E8E77; Sun, 29 Sep 2013 08:29:11 +0000 (UTC) (envelope-from adrian.chadd@gmail.com) Received: from mail-wg0-x22e.google.com (mail-wg0-x22e.google.com [IPv6:2a00:1450:400c:c00::22e]) (using TLSv1 with cipher ECDHE-RSA-RC4-SHA (128/128 bits)) (No client certificate requested) by mx1.freebsd.org (Postfix) with ESMTPS id D0EDA2BC4; Sun, 29 Sep 2013 08:29:10 +0000 (UTC) Received: by mail-wg0-f46.google.com with SMTP id k14so4237375wgh.13 for ; Sun, 29 Sep 2013 01:29:09 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20120113; h=mime-version:sender:in-reply-to:references:date:message-id:subject :from:to:cc:content-type; bh=j1D3XnFSZTBTyrhF3liZkbhTSIkvK2eDgKVCbHEJk3Y=; b=ixeAtDvj/I7Ys6SHcb49yTszNN1PwbyB0DlUh/TVG9/Szk/aYsyfChUKU+fNsNqw0g jE+yl2c736Xf88NwZj4ZlRFh9E8KFcBPwLkVB5bKM0QpG0WIvKe1rSiotglpBWri+gfS z6q6acvzk8/H7/pWLigZyhtZM8NRy9fcl9oagSsxPVKAlve1veeUQ7sBumv1r7IPzgJO nNlxOkLsuqRkX5IdqD75mGH4AQUNfZ5ms6LJ3MuQ+vrlxjZjYV39elTupXpf5HIjY7hb kiUXUcyt4ZurvThnftnklKSDA+gxcgwRqundjmkw1JRcIfK0hX2Ti1hO6IjCNBBXhZ+B gi8Q== MIME-Version: 1.0 X-Received: by 10.180.211.206 with SMTP id ne14mr9210711wic.30.1380443349365; Sun, 29 Sep 2013 01:29:09 -0700 (PDT) Sender: adrian.chadd@gmail.com Received: by 10.216.73.133 with HTTP; Sun, 29 Sep 2013 01:29:09 -0700 (PDT) In-Reply-To: <1380376595.1197.309.camel@revolution.hippie.lan> References: <20130928103758.GC27231@server.rulingia.com> <1380376595.1197.309.camel@revolution.hippie.lan> Date: Sun, 29 Sep 2013 01:29:09 -0700 X-Google-Sender-Auth: _WTBFxYR-Op5c5F6f2T5wb8Uzv0 Message-ID: Subject: Re: Mixing amd64 kernel with i386 world From: Adrian Chadd To: Ian Lepore Content-Type: text/plain; charset=ISO-8859-1 X-Content-Filtered-By: Mailman/MimeDel 2.1.14 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: Sun, 29 Sep 2013 08:29:11 -0000 +1. On 28 September 2013 06:56, Ian Lepore wrote: > 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. > Yeah, if there's PAE issues in -HEAD (read: there are, and we should fix the bugs that alfred/andre's autotuning stuff introduced) then we should fix it. PAE should still be working! -adrian