RFR (M): JDK-8065993: Merge OneContigSpaceCardGeneration with TenuredGeneration

[Kim Barrett]

[resending with correct from address, so it will go to list]

On Dec 1, 2014, at 7:42 AM, Bengt Rutisson <bengt.rutisson at oracle.com> wrote:
> 
> Could I have a couple of reviews to this cleanup?
> 
> http://cr.openjdk.java.net/~brutisso/8065993/webrev.00/
> 
> https://bugs.openjdk.java.net/browse/JDK-8065993

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src/share/vm/gc_implementation/concurrentMarkSweep/concurrentMarkSweepGeneration.cpp
2815 // YSR: All of this generation expansion/shrinking stuff is an exact copy of
2816 // TenuredGeneration, which makes me wonder if we should move this
2817 // to CardGeneration and share it...

[Comment was updated to refer to TenuredGeneration.]

Perhaps there should be a bug report for this cleanup?  I did a brief
search and didn't find one.

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src/share/vm/memory/generation.hpp
 53 // The system configurations currently allowed are:
 54 //
 55 //   DefNewGeneration + TenuredGeneration
 56 //   DefNewGeneration + ConcurrentMarkSweepGeneration
 57 //
 58 //   ParNewGeneration + TenuredGeneration
 59 //   ParNewGeneration + ConcurrentMarkSweepGeneration

This pre-existing comment near a comment that was changed looks a
little stale.  Wasn't DefNew + CMS recently removed?

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src/share/vm/memory/space.hpp

Why ContiguousSpace declaring friend with OneContigSpaceCardGeneration
replaced by Space declaring friend with TenuredGeneration?  That
movement is surprising, and seems like it might indicate a bug
somewhere.

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Only the last item, about the friendship change, is directly relevant
to the proposed changes, which otherwise look good.