someone smarter than Dave Cutler
in [Device Drivers]
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From: Peter Flass on 30 Mar 2010 17:05 John Francis wrote: > In article <lcosn.20672$iu2.3907(a)newsfe15.iad>, > Pat Farrell <pfarrell(a)pfarrell.com> wrote: >> Jonathan de Boyne Pollard wrote: >>>> _Showstopper_ mentions this. >>>> >>> I'm going to have to read that, someday. >>> >>>> Cutler had to be dragged kicking and screaming into allowing some >>>> paging of the kernel. >>>> >>> I wonder how much of the stick that Dave Cutler gets is completely >>> justified. >> IMHO, a lot. He had blinders on the topic of modern memory management. >> The Tenex/Tops-20 folks had it right, and they were all DEC. Now at the >> time, DEC was not really a single company, so a bit of the NIH spirit >> made sense from a corporate view. >> >> But his decisions hurt both VMS and NT, or rather his lack of experience >> in the state of the art. And in some cases, the start of the art we are >> talking about is 1969 art, implemented in the late 70s for VMS and late >> 80s for NT. > > I don't believe it was ignorance as much as it was a deliberate choice. > I always describe Cutler as having 20/20 tunnel vision - he knew what > he considered to be most important, and focussed on getting that done. > Other stuff that was just less important didn't get any attention. Maybe it was just hyper-caution. No one knew ho big NT was going to be, and no one knew what the effect of paging kernel code would be. Once there was a running system people could play with it and try out things like that.
From: Joe Pfeiffer on 30 Mar 2010 17:14 glen herrmannsfeldt <gah(a)ugcs.caltech.edu> writes: > > Well, there wasn't much of the microprocessor revolution in > 1974, which was when I read DATAMATION. The only one I actually > remember reading was about a PL/I compiler with a COME FROM statement. I remember that features as turning up in an April issue of SIGPLAN Notices in the late '70s... -- As we enjoy great advantages from the inventions of others, we should be glad of an opportunity to serve others by any invention of ours; and this we should do freely and generously. (Benjamin Franklin)
From: Johnny Billquist on 30 Mar 2010 17:25 Pat Farrell wrote: > Jonathan de Boyne Pollard wrote: >>> _Showstopper_ mentions this. >>> >> I'm going to have to read that, someday. >> >>> Cutler had to be dragged kicking and screaming into allowing some >>> paging of the kernel. >>> >> I wonder how much of the stick that Dave Cutler gets is completely >> justified. > > IMHO, a lot. He had blinders on the topic of modern memory management. > The Tenex/Tops-20 folks had it right, and they were all DEC. Now at the > time, DEC was not really a single company, so a bit of the NIH spirit > made sense from a corporate view. > > But his decisions hurt both VMS and NT, or rather his lack of experience > in the state of the art. And in some cases, the start of the art we are > talking about is 1969 art, implemented in the late 70s for VMS and late > 80s for NT. Not ever have been close to Dave Cutler, I can only reflect on some properties of RSX and VMS, of which I have some experience. Cutler seems to have been more focused on micro-kernels, which would lead to a design where you do not want or need paging in the kernel. Things which would bloat the kernel, and motivate having a pageable kernel are outside of the kernel in RSX and VMS. Things like file system code are in a separate process, for instance. Process context in VMS is pageable, including even the page table for a process. Now, microkernels did come into fashion later on, and is once more very much hot now. You want to load/unloade modules, drivers and whatnot in a running kernel, and not configure that statically before even booting. And the kernel wants to be small (but I haven't seen a single one who actually is, in my mind). Of course, how you design things are always based on what your targets are. Cutler was/is definitely not unfamiliar with the wish and requirements of having a small footprint of a kernel. RSX stands as a very good testimony to that. As far as I can tell, DC seems to be able to rub a lot of people the wrong way. No denying that. But giving him the stick for his technical abilities are usually more because he did things in a different way than the PDP-10 crowd at DEC. Something they seem to never forgive him for. But the technical merits in the attacks seldom seem to be very high. Sorry, but that's my point of view. And I happen to like TOPS-20 too, in addition to RSX. And I think there are some things that are very nice about VMS as well. Johnny -- Johnny Billquist || "I'm on a bus || on a psychedelic trip email: bqt(a)softjar.se || Reading murder books pdp is alive! || tryin' to stay hip" - B. Idol
From: glen herrmannsfeldt on 30 Mar 2010 17:38 In alt.sys.pdp10 Johnny Billquist <bqt(a)softjar.se> wrote: (snip) > Things which would bloat the kernel, and motivate having a pageable > kernel are outside of the kernel in RSX and VMS. Things like file system > code are in a separate process, for instance. Process context in VMS is > pageable, including even the page table for a process. When I was an undergrad I did a paper for a CS class, essential a compare and contrast for VAX/VMS paging vs. IBM OS/VS2 paging. VAX uses pagable page tables, IBM uses segments and pages, with pretty much the same result: two levels of virtual storage. The IBM z/Archtecture, 64 bit extension of S/370, has five levels of virtual storage, though some are bypassed for current memory sizes. -- glen
From: Mark Crispin on 30 Mar 2010 18:09
On Tue, 30 Mar 2010, Jim Stewart posted: > Mark Crispin wrote: >> On Tue, 30 Mar 2010, Jim Stewart posted: >>> Anyone that takes the time to leaf through some >>> Datamation magazines of that era would be lucky >>> to find any reference to PDP-10's. >> Using Datamation as an historical reference is like using the National >> Enquirier. > A circular religious argument not unexpected from > someone that believed that PDP-10's dominated the > era. So enlighten us about the IBM S/360 systems used to build the Internet. Tell us how such tools as document processing and email were invented on S/360. Tell us about how the world's timesharing was on TSS/360, Call-OS, and APL\360. Tell us about the seminal work on symbolic algebraric manipulation and artificial intelligence done on S/360. Oh, and tell us how S/360 launched the computer game industry with such programs as adventure and zork. Apparently, in the world of Jim Stewart, everybody used S/360 until they switched to Windows. -- Mark -- http://panda.com/mrc Democracy is two wolves and a sheep deciding what to eat for lunch. Liberty is a well-armed sheep contesting the vote. |