[jira] Updated: (HARMONY-1428) [DRLVM] first batch of files for GCv5, a trace-forward copying collector

["Xiao-Feng Li (JIRA)" <ji...@apache.org>]

     [ http://issues.apache.org/jira/browse/HARMONY-1428?page=all ]

Xiao-Feng Li updated HARMONY-1428:
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    Attachment: gcv5-r0.10.zip

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 are welcome!

-xiaofeng

> [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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