Re: [Jikesrvm-researchers] Just tracing the pointer-update related bytecodes is not enough?

[Matthew H. <he...@ca...>]

The way that Merlin is implemented in the Jikes RVM, it performs a complete root
scan at each accurate point in the trace.  This root scan includes both a scan
for references in the threads stacks and a scan for all of the references in the
JTOC (static region).  While there are hooks in place for the implementation to
take advantage of a write barrier on the static fields (and therefore omit the
scan of statics at each accurate point), it is not relying on these at the moment.

In my initial implementation of Merlin (in Jikes 2.0.3 using GCTk), I also
created a stack barrier that performed a limited stack analysis at the method
call granularity.  I have not brought this forward, however, because of the
complexity of implementing this code (and sheer number of classes and subsystems
it impacts).

Thanks!

Sincerely,
Matthew Hertz

Li Gen wrote:
> Professor  Eliot Moss,
>         Thank you for your answer.
>         The academic of Merlin is prefect, and, of course,
> has considered references from stack (and registers) and from statics.
> But my puzzle is about the implementation of Merlin in RVM.
> In BaseBaseGCTrace of RVM 2.9.0, the implementation of static field
> write barrier is empty, and the baseline compiler does not implement the
> stack writer barrier in  emit_astore function, because the astore byte
> code is the only instruction which can save object references to the
> stack. So I mean, Merlin in RVM 2.9.0 can't know  when the object
> referenced by stack is updated, Am I right? And is there other reason
> for the unimplemenation of the stack write barrier?
> Best wishes
>  
>  
> 
> 
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