Re: VM images and working in the VM image

On 12-May-07, at 7:30 PM, Ted Neward wrote:

>
> (When you
> change the shape of objects in memory, though, how does the ST  
> image handle
> that? Do existing objects receive the change? And what happens if  
> methods
> are invoked in the middle of the reload?

Of course objects that are instances of altered classes change; to do  
other wise would be lame.
Methods are invoked by the gazillion during class changing package  
loads; since the loading is done by methods running how could it be  
otherwise? There's no magical stuff going on - a file is opened, the  
new code is read in, each method is compiled and installed and in use  
immediately.

> (*) How do you persist those changes to the image so that if the  
> machine
> crashes, the image doesn't lose all those changes? Do you  
> periodically have
> to flush the image to disk? And is that transactional somehow?
Yes, you save the image. Saving an image is (at least conceptually)  
an atomic operation (ask me about a major, major bug-emergency a  
major corporation caused by violating that rule) that, yes,  
interrupts everything for a moment.
>
> (*) Hopefully you'll also allow me to assert that running a blog  
> engine
> isn't exactly the high-scale requirement environment that some of  
> the Java
> (and .NET) app servers are asked to handle. :-) What I'd *really*  
> love,
> though, in order to move this particular point out of the realm of the
> abstract, is to know *exactly* what the runtime footprint of your "app
> server image" takes up, so as to hopefully compare/contrast it  
> against the
> runtime footprint of a Java app server stack. (I'd much rather  
> argue facts
> than assertions, and numbers against "belief".)

Take a look at Seaside/Pier related websites. Really. There is a lot  
of information already out there about Smalltalk. Answers to more  
questions than any one person could possibly have.

tim
--
tim Rowledge; [email protected]; http://www.rowledge.org/tim
Fractured Idiom:- VISA LA FRANCE - Don't leave chateau without it



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