[unios] Re: Kernel/Reflection

[Anders Petersson]

From: Anders Petersson <anders.petersson@mbox320.swipnet.se>

>From: Pieter Dumon <Pieter.Dumon@rug.ac.be>
>> From: Tril <dem@tunes.org>
>> Pieter wrote:
>> 
>> > I think you should really seperate the kernel design from the design of
>> > the higher-level OS services. 
>> 
>> Excellent.  I like this.  Let me restate it with emphasis added:  The
>> *design* of the kernel should be separate from the *design* of the
>> higher-level OS services.  In other words, we shouldn't design the high
>> level OS services around the kernel.  Instead, the high level OS
>> services (including programming languages) should control the kernel, its
>> design and implementation.  
>
>I disagree. The kernel controls everything. That's what makes a system
>stable. Some processes can be given control over the kernel's run-time
>configuration etc, but that's all. 

And I disagree with Pieter. The kernel should control as little as
possible, to allow for maximum flexibility/scalability. Ultimately, there
should be no kernel, but I doubt that is possible.

>> That's called reflection.  It's a main feature of TUNES (in big letters at
>> the top of our web page, www.tunes.org).  When it is strongly supported by
>> a system, a "kernel", or centralized static controlling unit, can be made
>> into a decentralized dynamic SLAVE unit, that is, power to the user to
>> completely reconfigure the topology of information flow in the system.
>
>It gives power to he user indeed. Too much. A good old microkernel gives
>power to the user too, but that power is controled by the kernel. That's
>why I want a kernel.

*Too* much power? I don't think that is a logic argument, unless there are
negative side-effects. I advocate separation of policy from mechanism. The
kernel should not impose "hardwired" policies, its function is to provide
the mechanisms. Policies are instead dealt with by the system that is built
round the kernel (or other low level constructs).

>> Basically the kernel warps itself to new configurations based on resources
>> available and user choices.  Reflection is the ultimate flexibility!
>
>Yes, you can give some processes control over some kernel features, but
>that's up to the kernel and the initial control processes.

Kernel - mechanism
Processes - policy

binEng



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