RFR(S): 8011724: G1: Stack allocate instances of HeapRegionRemSetIterator

[John Cuthbertson]

Hi Everyone,

Can I have a couple of reviews of these changes: 
http://cr.openjdk.java.net/~johnc/8011724/webrev.0 ?

Summary:
I've changed RSet scanning to stack allocate instances of the 
HeapRegionRemSet iterator and removed the pre-allocated instances 
(created during heap initialization).

Testing:
GC test suite with MaxTenuringThreshold=0, IHOP=1, and VerifyAfterGC to 
create a lot of old data.; jprt.

Thanks,

JohnC