What Is FFI

Robert Withers withers at vnet.net
Tue Feb 8 00:15:26 UTC 2000


"Raab, Andreas" wrote:
> 
> > Gruess Gott!  This sounds very cool.  I had a thought though.
> > Why don't we split the job between 2 VMs, with some shared
> > memory, and let theother VM be the one that crashes.
> > Be able to detect and log it, and restart another VM.
> > Flag that call as disabled and keep going?
> 
> Interesting idea. There are a couple of problems with it though. The biggest
> problem is that Squeaks object memory can be corrupted by calls to external
> functions. There is no way to check this and the effect is not immediate
> (e.g., usually the system will crash at the next garbage collection and this
> may be *way* after you've actually done the bad stuff). Thus, you would
> basically need to clone the entire image for each call (ouch) until you know
> it's in a stable state again. And not only the image - it can be similarily
> bad if you corrupt any VM state so you'd basically have to clone the entire
> process (e.g., VM+image). A little too much work just for calling some
> function ;-)

Yes that would defeat the purpose but we don't have to use shared
memory.  Actually Linda, as soon to be, will run in another VM adn you
can do copies with (hopefully) remote monitors so you can tell when
memory is gone or the other side crashed.  Run the VM in the main
process and launch helper vms that can attempt the dangerous stuff.  I
guess the idea that I forgot to mention above is having RemoteRefs to
objects so you can fault across what you need.  I think I saw some
Squeak RMI code somewhere and the Minnestore database does a cool job
with having ghosts in place of ivars, such that you can control how much
you fault in and demand load other stuff as needed.  

Yeah, it would be a lot of work! ;)  I don't know if I could help much
other than try my best to get Linda dancing.  Camp Squeak could make for
an interesting deadline...

On another topic:  has anyone managed to get some high res VR goggles
working as display (say Alice?).  I'd just love to see something like
that at Camp Squeak! 

-Rob
 
-- 
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Smalltalking by choice.  Isn't it nice to have one!





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