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From "Weldon Washburn" <weldon...@gmail.com>
Subject Re: [DRLVM] write barrier -- some preliminary design ideas for Jitrino.JET
Date Wed, 14 Jun 2006 15:44:23 GMT
Alex,
It looks like the JIT needs to support write barriers written in both
C as well as Java.   Its probably best to think of the C write barrier
as a conventional vm helper call.  For a garbage collector written in
Java like MMTk, the write barrier is actually Java code.  Injecting a
vm helper call and crossing the JNI boundary twice per each MMTk write
barrier will be a nightmare to debug.  Most likely performance would
be unacceptable even for debug.


On 6/14/06, Alex Astapchuk <alex.astapchuk@gmail.com> wrote:
> I'm not too familiar with GC stuff, but seems you are right and your
> patch fits all.  In case of AASTORE for .jet, as it generates a helper
> call anyway, the VM can do the job. The statics are all known for GC
> so they can be easily scanned. (Can GC guys comment on this ?)

For a general purpose GC/VM interface, it is best not to assume the GC
algorithm will always scan all the static variables containing
reference pointers.  The write barrier needs to also be applied to
putstatic.
>
>
> --
> Thanks,
>   Alex

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