>From: tim Rowledge <tim at rowledge.org>
>Reply-To: The general-purpose Squeak developers 
>list<squeak-dev at lists.squeakfoundation.org>
>To: The general-purpose Squeak developers 
>list<squeak-dev at lists.squeakfoundation.org>
>Subject: Re: Preemptive scheduling
>Date: Tue, 1 May 2007 13:24:30 -0700
>
>>On a real OS
>
>...interesting definition of 'real' here. I can assure you there are  OSs 
>I've used that didn't do any such thing...

Ok fine, change the word 'real' for 'modern'.  Of course there used to be 
batch systems, cooperative systems, and so on, but modern server/desktop 
OS'es behave this way.  Better? :)

>You can easily do this in Smalltalk in a portable way; just a high  
>priority process that cycles on a time interrupt to shuffle the  process 
>scheduler. You can manually shuffle the processes at the  various 
>priorities if you want to.

I'm good with a time interrupt, but how is that done in a remotely 
portable/safe way?  I'm not asking about process shuffling, I'm asking how a 
process that consists of:

[ [ true ] whileTrue: [ true ] ] fork

can ever be taken off the processor.  Unless you do either (a) instruction 
count based preemption or (b) time based (i.e. what CPU's use), it can't be 
done afaik.

>If you want to do some sort of count of bytecodes or prim calls  instead of 
>a simple timer, that is not difficult to arrange. I think  John put some 
>timer/counter stuff in a few years ago that would  support this.

I only suggested bytecode count because I didn't realize there was a good 
way to do timebased (which would actually be the prefered method if 
possible).

>I'm not sure; to be honest there seems little point in trying to make  
>'Smalltalk be the OS' for practical systems. What is probably much  more 
>sensible is to make Smalltalk do much better at integrating into  the OS so 
>it has more general value. In some respects Spoon is making  a very good 
>pass at this. The cost is that for every bit of OS  integration you provide 
>the cost of porting goes up enormously.

This is what I am wondering though.  If integrating Smalltalk better into 
the OS is taken to the extreme you end up with a Ruby with prettier syntax.  
I think a lot of power is there to be had by having a mini-OS.  As you 
mentioned, portability is one of these benifits.

Looking at things from the point of view of writing scripts, it may seem a 
bit inconvenient having a mini-OS VM.  But looked at from a very large, 
distributed, multi-core, multi-OS architechture point of view, I personally 
see a different picture.  I see Yaws (a system that doesn't seem to 
integrate so well with other systems) absolutely smoking Apache (a system 
that integrates with anything) at the high end.

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