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From "Weldon Washburn" <weldon...@gmail.com>
Subject Re: [DRLVM] proposal to port MMTK to drlvm
Date Wed, 24 May 2006 22:16:49 GMT
On 5/24/06, Rodrigo Kumpera <kumpera@gmail.com> wrote:
> Note that read barriers are also needed if you want to implement a GC
> like Baker's real time copying collector that uses incremental
> forwarding.
Rodrigo, good point.  For initial MMTK bring up, I would like to keep
things as simple as possible.  How about ignoring read barriers until
after initial bring up?  Also, those on the mailing list who are
interested in read barriers should feel free to jump in.

>
> Rodrigo
>
>
> On 5/24/06, Weldon Washburn <weldonwjw@gmail.com> wrote:
> > On 5/24/06, Ivan Volosyuk <ivan.volosyuk@gmail.com> wrote:
> > > I have a patch for drlvm which enables use of write barriers. This
> > > works in interpreter mode only yet. I can put it on jira if somebody
> > > is interested.
> > This is helpful.  Please post the patch.  I will take a look at it
> > sometime soon.
> > Thanks
> >
> > >The write barriers are tested with an algorithm which
> > > does per-slot validation and should work fine.
> > > --
> > > Ivan
> > >
> > > 2006/5/24, Daniel Feinberg <csdread@gmail.com>:
> > > > > >My understanding of write barriers is as an optimization.
> > > > > That fits with my understanding of write barriers also.   I do not
> > > > > know for certain but suspect that MMTK can somehow be configured
such
> > > > > that write barriers are not required for correctness.  Maybe Dan
> > > > > Feinberg can tell the mailing list.
> > > >
> > > > So MMTK is a toolkit for building GCs. When doing generational
> > > > collection the write barrier is used to keep track of pointers that go
> > > > from older generations to yonger generations. You must have a way to
> > > > track these objects because when you do a partial heap collection (aka
> > > > just the nursery or nursery and old1) you need to build a root set of
> > > > all things that point into that space. Then you trace this root set to
> > > > find all live objects that need to be moved to an older generation. In
> > > > other methods of collecting the write barrier is not as important.
> > > > Here unless you can find all of these pointers that point into a space
> > > > from an older space you must use a write barrier.
> > > >
> > > >
> > > > Daniel
> > >
> > > ---------------------------------------------------------------------
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> > >
> > >
> >
> >
> > --
> > Weldon Washburn
> > Intel Middleware Products Division
> >
> > ---------------------------------------------------------------------
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> >
>
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>


-- 
Weldon Washburn
Intel Middleware Products Division

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