[Vm-dev] An event driven Squeak VM

[Jecel Assumpcao Jr]

Bert Freudenberg wrote:
> On 10.11.2009, at 09:00, Andreas Raab wrote:
> 
> > ... make the Squeak VM be "truly event driven" that is invoke it in response to OS or other events instead of having the VM poll. 
> 
> Don't have time to really get involved but I like the idea :)

I am interested as well. On a related issue, another programmer is
working on the "announcements for i/o events" idea we briefly discussed
in the beginning of the year.

About having the scheduler in the image rather than in the VM, that is
how Self does it. A friend of mine started his PhD thesis using Squeak
but switched to Self because of this feature even though I showed him
that you could use a few tricks to change the behavior of the Squeak
scheduler in interesting ways (I have implemented real-time scheduling
with stuff like first-deadline-first, rate monotonic and so on using a
higher priority thread waiting on the timer as the actual scheduler).

About to pros and cons of having platform dependent code in the image,
there is an interesting discussion in the "Dorado" chapter of the green
book. My proposal to the SqueakNOS group was that we could have two
images: a small headless one with all the SqueakNOS drivers and
primitives and a normal one with the user application. The second image
would send messages to the first one for all its i/o so no code would
directly access the hardware. In practice, you have the same protection
as if there low level stuff were in the VM (or some underlying OS) and
the image stays clean of any platform dependency. But if you really know
what you are doing, you can call up remote debuggers, inspectors and
browser on the first image and it will feel like all this stuff is
implemented in the image instead of the VM.

-- Jecel