RFR (S): 8037344: Use the "next" field to iterate over fine remembered instead of using the hash table

[Jesper Wilhelmsson]

Looks good.
Thanks for cleaning up the comments!
/Jesper

Thomas Schatzl skrev 14/3/14 17:41:
>
> Hi all,
>
>    could I have reviews for this small change that cleans up the
> HeapRegionRemSet-iterator?
>
> The reason for this change is that in JDK-7182260 linked together all
> PerRegionTable data structure (representing parts of the fine remembered
> set) of a fine remembered set for a particular region. However the iterator still walks the hash table.
>
> I took the opportunity to try to slightly improve the documentation of
> the HeapRegionRemSetIterator (comments) as the change changes the
> HeapRegionRemSetIterator interface already anyway.
>
> A micro-benchmark that does nothing for every card indicates that
> iterating of the PRTs got a lot faster (mainly due to the less
> complicated check in HeapRegionRemSetIterator::fine_has_next() I assume) and is only a side-effect of the change.
>
> CR:
> https://bugs.openjdk.java.net/browse/JDK-8037344
>
> Webrev:
> http://cr.openjdk.java.net/~tschatzl/8037344/webrev/
>
> Testing:
> jprt, specjbb*, specjvm2008*, dacapo and other benchmarks having large
> remembered sets.
>
> Thanks,
>    Thomas
>
>