[self-interest] multiple VMs (was: desnarfing tinySelf)

Jecel Assumpcao Jr jecel at lsi.usp.br
Wed Apr 28 06:12:01 UTC 1999

> > [selecting one from multiple VMs in a Snapshot]
> I like this idea, but what about the potential bloat caused by the presence
> of all of those conveniently present VMs?  We could just keep them there in
> the image (maximum portability and convenience), or we could have this
> little boot program strip out the uneeded ones, once the correct VM is
> determined.  This option could be presented to the user on first start-up.

You are quite right, since I didn't explain that I want to break
up the Snapshot file into much smaller chunks (files). You won't
have to load the chunks you don't need (those containing VMs for
other systems, for example) into memory. In fact, you shouldn't
even have to have these chunks on your disk. But as long as they
exist somewhere in the world, they are logically a part of a virtual
"world wide Snapshot" and can be downloaded from the net if ever
called for.

Aren't we back to where we started, with several VMs each one in
their own separate file? Not quite - in the original situation the
VMs and their Snapshots were bound together manually by the user
with possibly a little help from the OS. In my idea there is a
mechanism which binds all the chunks together into a single logical
Snapshot and I use the exact same mechanism to associate the correct
VM with that logical Snapshot - the underlying OS is not involved at

> Any idea how big a typical VM might be?

Self 4.0's VM is 2MB, but it includes a *lot* of stuff I feel should
be moved out of there. Squeak's VMs tend to be from 150KB to 250KB.
It is just a simple interpreter instead of two full compilers, but
it does include a lot of primitives for graphics and sound (while
the Self 4.0 VM just has a little glue code and lets X Window do
all the graphics).

-- Jecel

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