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From Aaron Hamid <ar...@cornell.edu>
Subject Re: [arch] VM Candidate : JikesRVM http://jikesrvm.sourceforge.net/
Date Fri, 20 May 2005 13:57:31 GMT
As a purely idle bystander and armchair speculator, I'm with Steve on this one.  It seems the
community has roughly aggregated into "VM in Java" and "VM in C/C++" camps.  Both camps appear
to have large and robust support and actual working implementations behind them.  In the former
I see "JikesRVM" and "JNode".  I think the Java-in-Java horse has been beaten to death and
hopefully we can agree that it is not only feasible, but works today and brings its own set
of benefits.  Likewise in the "VM in C/C++" camp there is GCJ "and friends" (which already
have a long track record and fresh ideas, and amicability with large established GNU projects),
as well as some respectable independent offers such as JCVM and MudgeVM.

Instead of shoehorning the two camps into one VM, how about accepting, for the meantime, two
somewhat independent lines of /investigation/.  I have doubts that a "universal framework
interface" could be applied to both implementations without lots of pain and impedence mismatch
(especially the boundary-crossing-problem), but I am sure that each can take what is applicable
from the other without having the other's set of interfaces forced on them.

In the end, it might turn out to be useful to have two independent implementations, possibly
front-ended by a, um, front-end.  I imagine the "VM in C/C++" may have characteristics that
make it more amenable to low-latency desktop use, while the "VM in Java" may have throughput
characteristics that make it more amenable to server side use (again, wild speculation on
my part).

Since it is (at least to me) entirely non-obvious yet what the ultimate architecture should
be, why not just let two investigations proceed in parallel with those parties interested
in the respective technologies participating under the umbrella of "harmony" instead of being
shut out because they happen not to prefer the language or architecture that has been pre-emptively


Nick Lothian wrote:
>>Last Friday, I made the following proposal:
>>In the context of the current discussion I'd like to 
>>re-advocate that proposal.  It is consistent with what 
>>Stefano has suggested.
>>To summarize:
>>1. Leverage existing momentum by seeding the project with two 
>>existing VMs 2. Leverage existing work by focusing on 
>>modularity of major reusable components (including components 
>>from outside of the seed VMs).
>>3. Concurrently design new VM cores.
>>Modularizing the seed VMs will provide the group with a great 
>>deal of insight into how new VM cores should be built.  I say 
>>"cores" for three
>>reasons: a) the cores will (by defn) be small, so with a 
>>modular framework, having multiple cores should be feasible, 
>>b) different cores can target different needs, c) we can 
>>explore different implementation strategies.
> +1
> After looking through the code of Jikes I'm voting for this proposal
> (and the use of Jikes as a seed VM) because 
> a) Jikes seems a fairly mature, and it appears somewhat modular already
> b) I am (much) more likely to be able to contribute to Jikes than a
> C-based VM
> I do have some concerns about the build process that Jikes currently
> has, but Steve has already spoken about addressing that.
> There are probably licence issues that would need resolving, too.
> This isn't meant as a negative vote against other VMs - Steve's proposal
> explicitly mentions working on other VMs in parrel. 
> If people were going to work on JCVM (for instance) then I would imagine
> some enhancements could be shared, particularly to the parts of JCVM
> written in Java. It would also enable us to understand the interface
> requirements between parts of the VM better than most of us currently
> do.
> Nick
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