Date: Fri, 15 Oct 1999 07:41:01 +1000 From: Peter Jeremy <jeremyp@gsmx07.alcatel.com.au> To: freebsd-arch@freebsd.org Subject: Multiple VAS [Re: The eventual fate of BLOCK devices.] Message-ID: <99Oct15.073701est.40324@border.alcanet.com.au> In-Reply-To: <199910141515.IAA35743@pau-amma.whistle.com> References: <447.939897820@critter.freebsd.dk> <199910141515.IAA35743@pau-amma.whistle.com>
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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
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