[unios] Re: Generic design. More comments

[Pieter Dumon]

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

> From: Anders Petersson <anders.petersson@mbox320.swipnet.se>
> 
> I think something inbetween method 2 and 3 would be good:

Perhaps, yes.

> >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 .  
> 
> Processes - Multitasking has to be low-level, since it's closely related to
> the kind of processor, if that's what you mean. However, processes are not
> concerned with the type of hardware.

No,no _threads_ have to be implemented by the kernel or whatever, because
it's teh thread's state that is being saved. A process is just a
collection of threads (abstracted by the kernel) and a memory space
(abstracted by teh kernel too).

> Memory management - Isn't this dependant (at least for resonable
> performance) on the hardware availible?

Well, the kernel abstracts the logical memory for each thread and does
the low-level managment, but virtual memory (swapping in and out pages)
can be provided by a user-level process, for instance.

> Drivers - Device drivers are  of course low-level... could you mention some
> examples of middle-level drivers?

Ah, that was an error indeed. But the drivers can run in user mode, that
was what I meant.

> mOS needs a kernel to implement the most basic stuff, like memory managment
> and system calls. The kernel need to be there, only that it is small and
> has delegated most jobs to ordinary processes.

We can use a "no-kernel" design. All hardware, so cpu and memory too,
is abstracted by an object each, running in a seperate memory space etc.
This would make it all very flexible, and probably stable, but not fast.

 
> > ------------------------------------------
> > | 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 don't like the idea... I want to make mOS the kernel.
>

mOS the kernel ? That would - hurt performance
			    - decrease flexibility.	
 
> No problem, it's quite clear, even if a bit low on color shades. :)

:-)))



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