Re: [rvm-research] Regarding Address of Object Reference in Field section of Object

Robin,

Thank you. I am looking at that code.  When I override objectReferenceRead
it seems like it is never called. I am trying to understand how it works.
Is there anything I have to do other than overriding that in my mutator
class?

Cheers
Hari Krishnan.


On Mon, Jan 13, 2014 at 11:47 PM, Robin Garner <[email protected]>wrote:

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> The MMTk plan "poisoned" unconditionally sets and clears the low-order
> bit of all object references - this is the regression test for object
> read and write barriers.
>
> cheers
>
> On 14/01/14 15:53, Hari Krishnan wrote:
> > Robin,
> >
> > The process is basically to mark the references as I trace the
> > objects. Since I want to mark the instance field references in each
> > object, I want to mutate a single bit indicating the reference is
> > processed.  So yes to question (you want to add a single bit of
> > metadata to each object reference ?).Thank you for your help. I
> > want to try Read Barriers. I appreciate your quick response. Is
> > there any code that  already overrides read barrier?
> >
> > Cheers Hari Krishnan.
> >
> >
> > On Mon, Jan 13, 2014 at 10:45 PM, Robin Garner
> > <[email protected] <mailto:[email protected]>> wrote:
> >
> > Hari,
> >
> > Just to clarify, you want to add a single bit of metadata to each
> > object reference ?
> >
> > The "simplest"[1] solution is to use one of the two low-order bits
> > of each object reference (objects are always (at least) 4-byte
> > aligned). In order to do this you'll need a read barrier that masks
> > out this bit so that the mutator always sees aligned pointers, and
> > a write barrier that reinstates the metadata.
> >
> > Alternatively, if this is too expensive, I'd suggest adding
> > additional space to the object via the classloader - how easy this
> > is depends on how you want to use the data, how much space you're
> > prepared to use etc.
> >
> > cheers
> >
> > [1] Read barriers are never simple :-/
> >
> > On 14/01/14 12:01, Hari Krishnan wrote:
> >> Hi ,
> >
> >> I want to set a bit, toggle a bit and test a bit in the section
> >> where each address of the instance field (object references)
> >> saved in objects. Is there any bit that I can use in each object
> >> fields for this purpose?
> >
> >> Cheers Hari Krishnan
> >
> >
> >
> >
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