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From "Simon Chow" <simon.harm...@gmail.com>
Subject Re: [drlvm][general] Multi-tasking VM?
Date Mon, 10 Dec 2007 10:34:34 GMT
On 10/12/2007, Xiao-Feng Li <xiaofeng.li@gmail.com> wrote:
>
> On Dec 10, 2007 5:02 PM, Simon Chow <simon.harmony@gmail.com> wrote:
> > Yes, I agree that.
> >
> > But I think MVM's feature of sharing class runtime representations
> across
> > applications' can make many apps benefit not only at startup phases, but
> > also at runtime.
>
> Yes. Runtime sharing could be useful. Without MVM, this can be made
> available through OS supports to dynamic shared objects (with careful
> design).


good idea!

> Besides these, I guess processes scheduling may be useful when running 2
> > related programs like server and database.
> > And migration Java processes between defferent JVMs would be useful for
> load
> > balance and reliability in distributed enviroment.
>
> I remember MVM was only for shared memory system, no support to
> distributed environment (unless you meant distributed shared memory
> system, but that's too far a concept).


I  means that maybe we can migrate a running "Java process" in a heavily
loaded JVM to a free JVM in another computer.
This may be similar to real process migration in different OS, AFAK, which
is difficult to implement.
But for Java, I think it will be more easily than that.

This is only my thought, maybe far from MVM. But it could be based on MVM.

Btw, please use the word
> "process" carefully, because the tasks in MVM are not the processes in
> traditional sense. My understanding of "process" is clearly the entity
> with address space isolation.



Thank you, I will remember that. :=)


> Ok, it may be useless idea in practice. But if all these things can be
> > achived just by MVM. Is it valuable to do it?
>
> The problem is, whether we want to achieve those benefits with MVM if
> they can attained through other approaches. In my opinion, the key
> concept of MVM is to share the same virtual address space between
> multiple JVM instances. But since the address space isolation with
> process has been well established, proven, and mature in current
> platforms, then how to share the space needs deep thinking and serious
> proving.


I saw the TODO Comments in method JNI_CreateJavaVM like this:
//TODO: only one VM instance can be created in the process address space.
Dose this mean what you said above? :)
I am interested how to do these just when I saw the comments.

Simon, it's good for you to think of these things. It's always
> encouraged. And my comments are only my personal opinions, just for
> your reference.
>
> Thanks,
> xiaofeng


Thank you Xiaofeng!
Btw, I heard about you from HuangBo when I told him I am working on Harmony
after his adv. compiler class.
What a small world!

> Thanks for your comments!
> >
> >
> > On 10/12/2007, Xiao-Feng Li < xiaofeng.li@gmail.com> wrote:
> > >
> > > On Dec 10, 2007 2:49 PM, Simon Chow <simon.harmony@gmail.com> wrote:
> > > > Acturally, I am just a greenhand for JVM.
> > > > After seeing some paper about MVM, which says MVM can reduce the
> startup
> > >
> > > > overhead and footprint of programs, I think both destop application
> and
> > > > server application can benefit from it.
> > > > In my opinion, at least, some IDE can use it for debugging small
> program
> > > > more conveniently by avoiding startup overhead.
> > > >
> > > > Could you say something about its shortage?
> > > > Thank you!
> > >
> > > Simon, I think the advantage (shorter startup time) of MVM you
> > > mentioned can be achieved without MVM. Don't you think so?
> > >
> > > Thanks,
> > > xiaofeng
> > > >
> > > > On 10/12/2007, Xiao-Feng Li <xiaofeng.li@gmail.com> wrote:
> > > > >
> > > > > On Dec 10, 2007 1:00 PM, Simon Chow < simon.harmony@gmail.com>
> wrote:
> > > > > > Will harmony support the multi-tasking feature?
> > > > > > I has seen that Sun has a project name
> > > > > > Barcelona< http://research.sun.com/projects/barcelona>which
> aimed to
> > > > > > run several Java applications on 1 JVM.
> > > > > > Maybe it can improve the JVM performance somehow.
> > > > > > I am very interested about this, but I can not find more
> resource
> > > about
> > > > > > this....
> > > > >
> > > > > In foreseeable future, Harmony might have no plan for MVM support.
> I
> > > > > had some investigations in this area, and I personally am not
> fully
> > > > > convinced by the idea.
> > > > >
> > > > > Thanks,
> > > > > xiaofeng
> > > > >
> > > > > > --
> > > > > > From : Simon.Chow@Software School of Fudan University
> > > > > >
> > > > >
> > > > >
> > > > >
> > > > > --
> > > > > http://xiao-feng.blogspot.com
> > > > >
> > > >
> > > >
> > > >
> > > > --
> > > >
> > > > From : Simon.Chow@Software School of Fudan University
> > > >
> > >
> > >
> > >
> > > --
> > > http://xiao-feng.blogspot.com
> > >
> >
> >
> >
> > --
> >
> > From : Simon.Chow@Software School of Fudan University
> >
>
>
>
> --
> http://xiao-feng.blogspot.com
>



-- 
>From : Simon.Chow@Software School of Fudan University

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