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From "Ivan Volosyuk" <ivan.volos...@gmail.com>
Subject Re: [drlvm] Jitrino.OPT performs incorrect GC enumeration in nested loop with array accesses
Date Fri, 06 Oct 2006 16:41:00 GMT
On 10/6/06, Mikhail Fursov <mike.fursov@gmail.com> wrote:
> On 10/6/06, Ivan Volosyuk <ivan.volosyuk@gmail.com> wrote:
> >
> >
> > I would like to have second variant implemented and corresponding
> > (method3) interface removed as unused anymore. But, I'm not sure if
> > this is possible. Thread stack enumeration  is just a part of root set
> > enumeration process. Roots can be already reported (and moved) even
> > before the jitrino enumeration starts. Will the second variant work
> > despite of this?
> Why do you think it will not work?
> Here is the algorithm
> JIT reports 2 types of items: 1) bases 2) mptrs + offsets
>  1)  Once JIT report base GC uses the same algorithm as before: it moves the
> object and for subsequent reports of the same base it uses 'forwarding
> pointer' as you mentioned before:
> " if the second reference points  to previous position of object it will be
> automatically updated  according to installed forwarding pointer."
> 2) When JIT reports mptr + offset, GC deduce the old object location, and
> uses the same 'forwarding pointer' to adjust the mptr
> What is wrong with this schema?

If it is possible to get somehow valid offset within object then it is
great! I would be happy to see this solved this way. Waiting for your

For, now I have attached to JIRA HARMONY-1682 the pessimistic variant
of fix for those who may not be interested in the discussion and wants
to have the problem fixed (workarounded?) anyhow.

> There is one more way to make this work. Do the same as gc_v4 does:
> > get full root set and then do the modifications to heap.
> >
> Yes this is the most pessimistic variant we have if all other variants
> failed
> --
> Mikhail Fursov

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