Re: Virtual Machines, JVM in kernel, hot-swapped kernel

Tomasz Rola (rtomek@cis.com.pl)
Tue, 25 Aug 1998 03:10:51 +0200 (CEST)


On Sat, 22 Aug 1998, Alexander Kjeldaas wrote:

> On Fri, Aug 21, 1998 at 02:19:48AM +0200, Tomasz Rola wrote:
> >
> > Also, I'm interested in JVM (Java Virtual Machine) built into the kernel.
> > Has somebody started this already on Linux? Yes, I know about Java
> > support in current kernels but it's in user space. I'm interested in
> > kernel-space one. How about other languages - Lisp, perhaps ?...
> >
>
> You don't want a VM in the kernel, but you might want a system level
> VM - a single VM used by all java-programs what will do caching and
> optimalization etc. Other than that, it is interesting to see if
> there are any new services needed by a VM that the kernel should
> provide. I know of one such service: user-level exceptions. Being
> able to handle a memory protection exception without the
> user->kernel->user context switches makes certain GC/VM-tricks much
> less expensive.

Well, perhaps I want it :-) right into the kernel. Don't take me too
serious, I'm very stubborn :-).

I have thought about some special kind of JVM. Its purpose wouldn't be to
serve user-level programs but rather to experiment with some concepts from
Operating Systems field, like distributed kernel. I can't imagime anything
beyond this at the moment. I even can't tell you why I need distributed
kernel - I simply don't know yet :-). OK, maybe it would be useful to do
some kind of clustering... If I had such kernel, I would try to use it for
something useful.

So, there should be no classes.zip, no exceptions (very probably) and all
you could use it to would be to write some parts of kernel in a (I think)
very portable manner. Or write some extensions to existing kernel.

In fact, it would be a portable assembler. But use of existing one is more
economical.

Another interesting point is to make modules in Java, so that other parts
of system could use them as normal. That would probably involve some extra
kernel hacking. Currently, I am not the kernel specialist...

Of course, after some additional hacking you could use it as a basis for
kaffe or something...

bye
T.

--
** Tomasz Rola          I am going to forward myself to /dev/null  **
**                      To check if data is really discarded there **
**                      Or is it a gate to another Universe...     **
** mailto:rtomek@cis.com.pl ,    http://www.cis.com.pl             **

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