RFR: More efficient next bitmap resetting for traversal

[Roman Kennke]

>> Looks wrong ...
>>
>> 1) You passed in traversalSet iter, then re-creates traversalSet itr
>> for each worker, so you reset the regions n_workers times.
>>
> Oops, my bad ... you do claim_next on passed in region iterator, that's
> correct.
> 
> Just remove
> 511     ShenandoahHeapRegionSetIterator iter(traversal_set);
> 

Yes, done.

>> 2) Should grab heapLock in reset_next_mark_bitmap_traversal()

No, I don't think so. ;-)

Incremental:
http://cr.openjdk.java.net/~rkennke/better-traversal-reset-bitmaps/webrev.01.diff/
Full:
http://cr.openjdk.java.net/~rkennke/better-traversal-reset-bitmaps/webrev.01/

Ok?

Roman