Request for review (S): 7037276: Unnecessary double traversal of dirty card windows

[Y. Srinivas Ramakrishna]

I'd like a couple of code reviews for:

7037276: Unnecessary double traversal of dirty card windows
http://cr.openjdk.java.net/~ysr/7037276/webrev.00/

Card scanning with ParNew and DefNew scavenges was collecting
dirty card windows in one method and then doing a retraversal
of that window in another method to clear the cards and iterate
over the refs on those cards. This double traversal was unnecessary,
since the collection of contiguous ranges, their clearing and the
iteration over the covered refs could all be done in a single sweep
over the cards covering the region of interest.

I also specialized some of the arguments to these calls,
made some internal methods private and renamed a few others
for greater clarity.

This is the second of a series of about 4 CRs aimed at eventually
fixing 6883834 (the last in the series). Stay tuned for some
more incremental rearrangements of related code in another
one or two subsequent CRs.

A quick performance measurement didn't show any appreciable
change in scavenge times as a result of this change, but more
careful performance measurements are in progress.

Tested with jprt, the test case for 6883834 and refworkload server.
Perf measurements with refworkload server in progress.

thanks for your reviews.
-- ramki