[unios] Re: Generic design. More comments

[Pieter Dumon]

From: Pieter Dumon <Pieter.Dumon@rug.ac.be>

> 
> From: Anders Petersson <anders.petersson@mbox320.swipnet.se>
> 
> > - A completely independent low-level part wich can run this system, 
> >   and Win32,POSIX,OS/2,DOS etc, as seperate subsystems:
> >
> >   pro : - very fast
> >         - stable : if one subsystem has problems, the others don't
> >                    depend.
> >         - flexible
> >         - independent low-level (not dedicted to one function)
> >   con : - not just one mid-level part of the OS 
> 
> You mean a bottom system that can run all these systems natively? That
> sounds very generic, but... all mentioned systems have to be translated to
> run on this virtual machine - a virtually impossible task.

Well, every OS implements a virtual machine. The above just means that all
subsystems run completely seperate on top of the kernel  , on top of the
basic services.
It is however, not a good system, because every subsystem would have to
implement its own file system, tcp-ip etc. In certain cases, this can have
advantages, but in most not.

> 
> >- A complete independent low-level part wich runs your systems, and
> >  your system can off course run POSIX,Win32,OS/2,DOS etc on top of it,
> >  together with its own API (Like NT)
> >  
> >  pro : - one mid-level part, your system, which runs the other mid-level
> >          parts
> >        - still very flexible
> >  con : - not as fast
> >        - other subsystems depend on the basic subsystem
> 
> This would lower performance for every system... just taking advantages of
> the former method out.

Well, with "not as fast", I meant not as fast as the first design, but it
is still pretty fast.
Actually, this is the best design, I think, because your system can
provide the file system, networking protocols etc, to the other
subsystems,so export it objects to the others. It represents certain
objects as files to the POSIX and Win32 subsystems,.... 

> >- A low-level that allready implements the basic parts of your system,
> >  so the low-level are objetcs too.
> >  
> >  pro : - fast
> >  con : - larger and less stable low-level
> >        - all mid-levels depend on the implementation of the basic
> >          "mid"-level system in the low level.
> >        - harder to develop low-level
> >        - low-level dedicated to your system.
> 
> This was about the way I thought about it. It would make my system faster
> (since designed for it from the beginning), and not affect the performance
> of other systems very much, compared to the first model (just another
> interface to the hardware).
> The low-level layer would indeed be bigger, including much of the
> mid-level... just like you said. This does however bring one advantage...
> mid-level functions can, if wanted, circumvent the low-level stage, going
> directly to the hardware, since it's a part of the hardware specific code
> anyway.
> It's still possible to create mid-level functions that are
> hardware-independant. Faster to develop, slower to run.

But it makes the system fragile and more difficult to develop:
Look at WindowsNT. All services run in the low level, and even in kernel
mode. Whenever MS tries to add something, this makes NT unstable. That's
the reason NT still uses DirectX 3 : if they would add newer DirectX
versions to NT, this would make NT unstable. Indeed, it would make your
system faster. That's exactly what MS did : up to version 3.51, the GUI
ran in user mode, but in NT4, they let it run in kernel mode, in the
executive. This makes the UI somewhat faster, but is really a big error in 
architecture design. It's why NT is so difficult to get stable.  
Whith low level, I mean really the LOW level, so only the basic services:
  - threads , cpu scheduling
  - memory spaces, memory scheduling
  - hardware access control
  - hardware interrupt control & handling
  - cpu exception control  & handling
  - inter-process communication.

Processes, memory management, drivers, file system, networking: it can
all be implemented by the middle level, the level that gives an OS its
functionality and provides the API for the high level and user .  

> I looked back at your definitions and saw you defined the kernel
> low-level... this would mean that in the first two models, at least *two*
> kernels are needed - one for the completely independant part, and one for
> this ('my' sounds so self-centered) design... it that really good?

Don't be afraid to sound self-centered :-) I know what is meant.
Your (how can I otherwise indicate it ?) design doesn't run as a "kernel",
but as a normal set of user processes, perhaps with somewhat more
privilege. This is the basic idea that led to the development of
microkernels, still the best architecture today. 

> >One more thing : you should think about a good name for your system.
> 
> I in fact already have a name for it, mOS (good or not). I haven't used the
> name, since I didn't want the system look like something that's already
> designed and implemented. And, we're working under the flag of UniOS.
> 
> If everybody agrees that this is the preferred system, we could just call
> it UniOS.
 
I think UniOS should be the name for the whole system : kernel,
subsystems, basic OS applications,etc. Your design can be part of UniOS,
but Win32 can be too...

I think this is the best desing: (hell, this costed me a lot of my
text-mode graphical capabilituies :-) )

 ------------------------------------------
 | OS & user objects (applications)       |  HIGH LEVEL
 ------------------------------------------ 
                 ||
                                           ---------------
 ----------- -------- -------- -------
 | POSIX/X | | Win32| | OS/2 | | DOS |
 ----------- -------- -------- -------
   ||           ||       ||      ||           MID LEVEL                      
 -------------------------------------- 
 |         mOS (unprivileged)         | 
 --------------------------------------
                   ||
 -----------------------------------------------
 | Drivers,network, file systems (unprivileged)| 
 ----------------------------------------------- 
      ||                                   ---------------
 -------------------------------------
 |        KERNEL (privileged)        |        LOW LEVEL
 -------------------------------------
                 ||
 -------------------------------------
 |            HARDWARE               |               
 -------------------------------------

I hope it's not confusing...

Pieter


----------------------------------------
 Pieter.Dumon@rug.ac.be               
                                      
 http://studwww.rug.ac.be/~pdumon     
 
 ICQ  : 12428974
---------------------------------------

------------------------------------------------------------------------
To unsubscribe from this mailing list, or to change your subscription
to digest, go to the ONElist web site, at http://www.onelist.com and
select the User Center link from the menu bar on the left.
------------------------------------------------------------------------
UniOS Group
http://members.xoom.com/unios