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From "Xiao-Feng Li" <xiaofeng...@gmail.com>
Subject [DRLVM][GC] first generational version of GCv5 is submitted
Date Fri, 06 Oct 2006 13:17:43 GMT
The submitted revision is downloadable in JIRA-1428 at:

Attached in this email is the gc.xml file I am using that replaces
existing one for building gc.

Below is the submission description:

Attached file gcv5-r0.10.zip is first version of the generational
mark-compaction GC for GCv5, which combines previous two submitted
collectors as planned. That is, a trace-forward collector for minor
collection and a mark-compaction collector for major collection. An
additon of a copying algorithm is also developed that copies nursery
live objects to mature space during a major collection.

This revision has subtantial improvement in threading part. Although
it's still single threaded collector, the framework for multithreading
is ready. Basically, it has mutators and collectors to model the
application threads and collection threads.

A major design concept in this revision that was not made very clear
in previous submissions is "space".  "GC" is a concept of a full (or
standalone) garbage collector design. One GC can have multiple spaces,
each of which can employ different "collection policy". With this
design idea in mind, the previous trace-forward GC is adapted to be
the collection policy for the nursery space, and the mark-compaction
GC is adapted to be the collection policy of the mature space.

As an embodiment of the design idea, GCv5 eliminates the global gc
variable in existing Harmony GC, and different space managements only
need to know a general gc data structure, instead of the generational
gc structure.

This revision has been tested on Windows with SPECJVM98. As the first
actual generational GC, any comments (or questions) are welcome!


> [DRLVM] first batch of files for GCv5, a trace-forward copying collector
> ------------------------------------------------------------------------
>                 Key: HARMONY-1428
>                 URL: http://issues.apache.org/jira/browse/HARMONY-1428
>             Project: Harmony
>          Issue Type: Improvement
>          Components: DRLVM
>         Environment: These files were only tested on Windows with VS.NET 2003.
>            Reporter: Xiao-Feng Li
>         Assigned To: weldon washburn
>         Attachments: gc_v5.001.zip, GCv5-mc001.zip, gcv5-r0.10.zip
> This archive has a couple of files implementing an early version of a trace-forward copying
collector for GCv5. It's only a starter with very basic functionalities. It is a generational
GC reqiures write barrier implemented in JIT. It was tested with JET, and ran SPECJBB2000
and SPECJVM98.
> The algorithm is depth-first tracing of From-space, and forwarding live objects to To-space
(It can forward part of the From-space). The To-space has no real management except for the
accomodation of forwarded objects and large objects. So the To-space is going to be replaced
by a mark-compaction GC, and the large objects will be managed by a LOS GC.
> In order to minimize the changes to other components of DRLVM, the codes here comply
with the original contract between GCv4 and other components. I also borrowed some routine
code from GCv4 to avoid repetitive labor work.
> GCv5 is under active development, so please expect quick and big changes to this submitted
code base. I will submit new codes from time to time when they are worth a submission. Any
comments or codes are more than welcome.

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