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From "Geir Magnusson Jr." <g...@pobox.com>
Subject Re: [drlvm] [jvmti] Question about JVMTI calling Java code
Date Thu, 14 Sep 2006 05:34:01 GMT

Rana Dasgupta wrote:
> Weldon,
>   It may be a little early to guard for architectural impact of large parts
> of the VM being written in Java? I don't think that we are quite there yet
> or need to consciously design to enable this till we have completed the 
> MMTk
> integration and done exhaustive perf work.

I dunno.  I wouldn't think we'd be doing for MMTk specifically, as 
that's unproven for production use (although it would be excellent to 
support it as an option for research work.

But in general, shouldn't week keep migration to a Java based VM in mind?

>   In addition to the more trivial thread related data  being accessible
> from C, to support ThreadGroup.Enumerate() etc. functions do we want a lot
> of additional state in the thread manager for this? It may have been 
> nice to
> be able to add some recursion detection/protection support to the JVMTI
> implementation, if not necessarily turning off events on all Java code. I
> think that some level of recursion protection in JVMTI or in JVMTI based
> agents is not uncommon.
> Thanks,
> Rana
> On 9/13/06, Weldon Washburn <weldonwjw@gmail.com> wrote:
>> >You might want to look closely at the code paths in the JVMTI
>> functions.  If
>> >the functions in question happen to be arbitrary Java code, then these
>> code
>> >paths could lead to many other parts of the JVM which in turn might be
>> >written in Java.  In the future the JIT runtime helpers or the GC may be
>> >written in Java.  For example, an innocent looking object new, poll for
>> GC
>> >or poll for preemption inside a JVMTI function could take the execution
>> path
>> >deep inside of MMTk, or as mentioned below, deep inside
>> java.util.concurrent
>> .
>> >Rather than develop a general solution at this point, it may make sense
>> to
>> >make all the data JVMTI needs to read/write accessible from C code.

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