[8u60] RFR backport of 8053998: Hot card cache flush chunk size too coarse grained

[Thomas Schatzl]

Hi all,

  can I have reviews for the backport of "8053998: Hot card cache flush
chunk size too coarse grained" for 8u60?

It did only apply with minor changes, so I need re-reviews. The problem
is that some non-ported change (removing ParallelGCThreads == 0)
requires an additional cast of the ParallelGCThreads variable (which is
uintx) to be comparable to an integer zero constant.

Note that this change is based on "8060025: Object copy time regressions
after JDK-8031323 and JDK-8057536" which is also out for review

Full 8u60 changeset:
http://cr.openjdk.java.net/~tschatzl/8053998-8u60/webrev.8u60/
Diff changest:
http://cr.openjdk.java.net/~tschatzl/8053998-8u60/webrev.8u60-fix/

CR:
https://bugs.openjdk.java.net/browse/JDK-8053998

Original change:
http://hg.openjdk.java.net/jdk9/jdk9/hotspot/rev/7894458add89

Testing: jprt

Thanks,
  Thomas