From owner-freebsd-arch Thu Oct 14 14:41:26 1999 Delivered-To: freebsd-arch@freebsd.org Received: from ns1.yes.no (ns1.yes.no [195.204.136.10]) by hub.freebsd.org (Postfix) with ESMTP id 5B73914BDC for ; Thu, 14 Oct 1999 14:41:22 -0700 (PDT) (envelope-from eivind@bitbox.follo.net) Received: from bitbox.follo.net (bitbox.follo.net [195.204.143.218]) by ns1.yes.no (8.9.3/8.9.3) with ESMTP id XAA16005 for ; Thu, 14 Oct 1999 23:41:22 +0200 (CEST) Received: (from eivind@localhost) by bitbox.follo.net (8.8.8/8.8.6) id XAA45371 for freebsd-arch@freebsd.org; Thu, 14 Oct 1999 23:41:21 +0200 (MET DST) Received: from alcanet.com.au (border.alcanet.com.au [203.62.196.10]) by hub.freebsd.org (Postfix) with ESMTP id 859E014BDC for ; Thu, 14 Oct 1999 14:41:11 -0700 (PDT) (envelope-from jeremyp@gsmx07.alcatel.com.au) Received: by border.alcanet.com.au id <40324>; Fri, 15 Oct 1999 07:37:01 +1000 Content-return: prohibited Date: Fri, 15 Oct 1999 07:41:01 +1000 From: Peter Jeremy Subject: Multiple VAS [Re: The eventual fate of BLOCK devices.] In-reply-to: <199910141515.IAA35743@pau-amma.whistle.com> To: freebsd-arch@freebsd.org Reply-To: peter.jeremy@alcatel.com.au Message-Id: <99Oct15.073701est.40324@border.alcanet.com.au> MIME-version: 1.0 X-Mailer: Mutt 1.0pre3i Content-type: text/plain; charset=us-ascii References: <447.939897820@critter.freebsd.dk> <199910141515.IAA35743@pau-amma.whistle.com> Sender: owner-freebsd-arch@FreeBSD.ORG Precedence: bulk X-Loop: FreeBSD.ORG On 1999-Oct-15 01:15:04 +1000, David Wolfskill wrote: >So IBM came up with an "interesting" concept... "data only" address >spaces: A program would run in one address space, and request that the >OS create a new address space for it to play in. The (first -- don't >recall the official term) AS would then denote a range within this new >AS, and cause data to be placed into it. It's not clear to me how a process using 32-bit (or 31-bit) pointers can access multiple 31-bit address spaces. However I look at it, you appear to need to issue a system call to get the kernel to change the page table mappings. And once you have to go into the kernel, you've lost a lot of the advantage. This is actually one area where the segmented IA32 architecture could have been useful. Unfortunately, Intel (IMHO) got it backwards (again) and segmented the single 32-bit VAS, instead of allowing each segment to describe an independent 32-bit VAS. Peter -- Peter Jeremy (VK2PJ) peter.jeremy@alcatel.com.au Alcatel Australia Limited 41 Mandible St Phone: +61 2 9690 5019 ALEXANDRIA NSW 2015 Fax: +61 2 9690 5982 To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-arch" in the body of the message