From owner-freebsd-questions@FreeBSD.ORG Thu Apr 9 17:24:50 2015 Return-Path: Delivered-To: freebsd-questions@freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:1900:2254:206a::19:1]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by hub.freebsd.org (Postfix) with ESMTPS id 272B0E5 for ; Thu, 9 Apr 2015 17:24:50 +0000 (UTC) Received: from mail-ig0-x235.google.com (mail-ig0-x235.google.com [IPv6:2607:f8b0:4001:c05::235]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (Client CN "smtp.gmail.com", Issuer "Google Internet Authority G2" (verified OK)) by mx1.freebsd.org (Postfix) with ESMTPS id DA174A91 for ; Thu, 9 Apr 2015 17:24:49 +0000 (UTC) Received: by igblo3 with SMTP id lo3so72684919igb.1 for ; Thu, 09 Apr 2015 10:24:49 -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=bOvTIzpCD1HZJrPaYBatWiG0tIvQzj6Pq5g9vRHDijs=; b=GPFwPNxZ5LDwRRv6Wzh2U6nNbSOxFfJljh6GPLnwGNndri8Z0Y/B4xalgyaDIu51hv L6ypiBp3blzj9Y74vJSxuceak93Rc8gZYqbU8MBRxPuoP/6ijL8KDWvUJKeaMYqZAuoZ 3dyJjZaZd3pTqdUGNiuwr0MTy7zCgD2bbZFlh7nPqaihcr98ilnLROgrmIHdj+SA+OFF sappFdpyC4XD5/olPkTH7Y66RHo/PuSrMlQGenW+lJV3XV9B7I03507mDB4qfdbEP5+Q jf3fy1JrfpnVX7yq5Ba4Hi4pvNRcQ6u1u3mtYmMR/tTjaf+Ssb3pHpSXflD2nJHESxMV K8zw== MIME-Version: 1.0 X-Received: by 10.50.97.105 with SMTP id dz9mr6337655igb.49.1428600289375; Thu, 09 Apr 2015 10:24:49 -0700 (PDT) Sender: adrian.chadd@gmail.com Received: by 10.36.17.194 with HTTP; Thu, 9 Apr 2015 10:24:49 -0700 (PDT) In-Reply-To: <55353.128.135.70.2.1428598688.squirrel@cosmo.uchicago.edu> References: <5526408F.1090005@asim.lip6.fr> <20150409114941.692910293a8120de4dafd400@yahoo.es> <20150409114906.6dd4379c@archlinux> <55264DC5.9070606@asim.lip6.fr> <55267A63.4040503@qeng-ho.org> <55269509.1080103@asim.lip6.fr> <55353.128.135.70.2.1428598688.squirrel@cosmo.uchicago.edu> Date: Thu, 9 Apr 2015 10:24:49 -0700 X-Google-Sender-Auth: NFz6w1sUEumpmdMHqOcf5m7xGGA Message-ID: Subject: Re: How FreeBSD manage more than 4GB on 32 bits architecture From: Adrian Chadd To: galtsev@kicp.uchicago.edu Content-Type: text/plain; charset=UTF-8 Cc: =?UTF-8?B?UGllcnJlLVl2ZXMgUMODwqluZWF1?= , FreeBSD Questions X-BeenThere: freebsd-questions@freebsd.org X-Mailman-Version: 2.1.18-1 Precedence: list List-Id: User questions List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Thu, 09 Apr 2015 17:24:50 -0000 On 9 April 2015 at 09:58, Valeri Galtsev wrote: > > On Thu, April 9, 2015 11:19 am, Adrian Chadd wrote: >> Hi! >> >> This sounds... very exciting. I'd start by taking a look at how PAE >> works - you may be able to reuse all those pieces and just implement >> more than the 4 bits of physical address space. The interesting bits >> of PAE aren't just the extension of the physical addresses, but all >> the management of mapping things into virtual address space as >> required. > > The only problem with all these exercises is: on 32 bit CPU box a single > process still can only have 4GB of address space (according to my > definitely not deep enough knowledge of kernel)... Well, whatever the kernel/user split is, sure. For some workloads that's fine; you just can't mmap a TB of memory. But there's nothing stopping you mmap'ing windows into a larger physical address space. I've done that before to get around limitations. -adrian