RFR: 8296768: Use different explicit claim marks for CLDs in Parallel and Serial GC [v2]

[Thomas Schatzl]

> Hi all,
> 
>   please review this change that implements the same optimization as [JDK-8295871](https://bugs.openjdk.org/browse/JDK-8295871) to use different claim marks for different full gc phases for Parallel and Serial GC. For both collectors I decided to clear all marks before full gc, but that is arbitrary. If you want this could be done at the end to the same effect.
> 
> Testing: tier1-5 (with JDK-8295871)
> 
> Thanks,
>   Thomas

Thomas Schatzl has updated the pull request incrementally with one additional commit since the last revision:

  Move CLD claim clear to the end of gc

-------------

Changes:
  - all: https://git.openjdk.org/jdk/pull/11092/files
  - new: https://git.openjdk.org/jdk/pull/11092/files/f72caa61..fa2b8ad0

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=11092&range=01
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=11092&range=00-01

  Stats: 13 lines in 3 files changed: 7 ins; 6 del; 0 mod
  Patch: https://git.openjdk.org/jdk/pull/11092.diff
  Fetch: git fetch https://git.openjdk.org/jdk pull/11092/head:pull/11092

PR: https://git.openjdk.org/jdk/pull/11092