[Beowulf] small-footprint MS WIn "MinWin"

Geoff Jacobs gdjacobs at gmail.com
Mon Oct 22 16:46:29 EDT 2007


Jon Forrest wrote:
> Geoff Jacobs wrote:
> 
>> Everybody take a moment to remember how Windows NT was supposed to be an
>> elegant, microkernel design.
> 
> At one point, in its early history, NT was a microkernel design.
> However, since hardware was much slower back then, Microsoft
> decided to break down and put some things, like graphics, that
> were initially in user-mode "servers" into the kernel.
> 
> There were some people who objected to this, saying that the
> original pure design resulted in a more reliable OS, since
> user-mode bugs couldn't crash the kernel. However, the pragmatists
> pointed out thohat many of these user-mode servers were so critical
> to the running of the OS that if a user-mode server died, then
> OS became unusable anyway, so what was the point in staying
> faithful to the microkernel mantra.
> 
> Of course, these days hardware is so fast that microkernels
> and VM hypervisors don't add enough overhead for most people
> to notice.
>
> Cordially,

Until NT4, most critical processes ran in user land. Microsoft did with
NT4 what Apple did with Mach -- move much of the critical system
processes, including graphics, into the kernel to boost performance (as
you said).

I never ran NT 3.5 back in the day, so I don't know what the reliability
numbers are like, but I can't imagine it could be worse than the early
service packs of NT4. Assuming that code quality is similar, NT 3.5
should have been quite a bit more resilient than NT4, but I just don't
remember. Certainly, QNX provides a good example of how reliable a
microkernel OS can be.

Anyway, anyone have examples?

Now, why did Apple go the same route. They essentially wrote an obsolete
operating system with Mac OS X. Why didn't they go microkernel? Of
course, Mach is a pretty horrible kernel to start with and was likely
only used because of the NextStep legacy. It basically wipes out any
performance gains from their high level of integration, but I guess they
didn't want to devote the resources to going fresh with something like L4.

-- 
Geoffrey D. Jacobs

To have no errors
  would be life without meaning
  No struggle, no joy
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