Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP Path: utzoo!mnetor!uunet!husc6!ut-sally!rice!titan!phil From: phil@titan.rice.edu (William LeFebvre) Newsgroups: comp.sys.amiga Subject: Re: The Next Generation Message-ID: <475@ra.rice.edu> Date: Mon, 23-Nov-87 15:25:37 EST Article-I.D.: ra.475 Posted: Mon Nov 23 15:25:37 1987 Date-Received: Thu, 26-Nov-87 22:21:06 EST References: <2785@megaron.arizona.edu> <5294@ccicpg.UUCP> <468@ra.rice.edu> <7731@g.ms.uky.edu> Sender: usenet@rice.edu Reply-To: phil@Rice.edu (William LeFebvre) Organization: Rice University, Houston Lines: 45 In article <7731@g.ms.uky.edu> sean@ms.uky.edu (Sean Casey) writes: >In article <468@ra.rice.edu> phil@Rice.edu (William LeFebvre) writes: > >[without providing a shred of supporting evidence] > >>Correct! But remember: Unix is a poor example of a virtual memory >>operating system, and SunView is a poor example of a Unix-based >>windowed environment workstation. > >My experience with the former has been the opposite. Perhaps Mr. LeFebvre >would care to support his statements with some proof. Ok. I'll be more specific. Berkeley 4.x Unix is a poor example of a virtual memory implementation. Do you want exmaples of what is better? How about VMS? Forget the lousy user interface---I'm talking strictly virtual memory handling. Does Unix use a working set model? Does it make any attempt to prevent humongous Lisp and Prolog jobs from destroying everyone's performance? Not in my experience. But VMS does. And what about swapping strategies? Some would argue that you don't need to handle swapping separatly from paging. I might be inclined to agree. But that's beside the point. BSD does swapping, but it allocates swap space using the "buddy block" system. Can you say "massive fragmentation"? I knew you could. When VMS gets memory constrained, it just gets slow, penalizing the larger proccesses. But when Unix gets memory constrained, it gets unusable! We have had horrible experiences here at Rice with just 10 people trying to use the same Vax 750 running BSD: the students are working on Modula II programs, they all use Gosling's emacs to edit, and two people cannot reliably compile at the same time. Even with 8 megabytes (the most memory you can put in a 750). And what about Mach? I'm sure that it will have pretty much the latest and greatest in a virtual memory implememtation. Unfortunately, I don't have more information about it. Do you think that all research work in virtual memory systems stopped when BSD came out? Come on! It only makes sense that something better exists today, simply because of progress in the field. This has really diverged. Forgive me. William LeFebvre Department of Computer Science Rice University