RFR: 8280396: G1: Full gc mark stack draining should prefer to make work available to other threads [v2]

[Thomas Schatzl]

> Hi all,
> 
>   can I have reviews for this change that fixes a significant performance problem with g1 full gc marking when the overflow queue is in use? Basically this case causes the threads never share their work from the overflow queue, resulting in very bad parallelization in some cases.
> 
> This is a problem that has been fixed already in [JDK-8152438](https://bugs.openjdk.java.net/browse/JDK-8152438), but when looking at this code on g1 and parallel full gc, they both showed that issue.
> 
> This is the change for g1.
> 
> The CR shows some numbers how bad this can be.
> 
> Thanks,
>   Thomas

Thomas Schatzl has updated the pull request with a new target base due to a merge or a rebase. The incremental webrev excludes the unrelated changes brought in by the merge/rebase. The pull request contains three additional commits since the last revision:

 - Merge branch 'master' into 8280396-g1-fullgc-stack-drain
 - Remove unused methods
 - Initial commit

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

Changes:
  - all: https://git.openjdk.java.net/jdk/pull/7175/files
  - new: https://git.openjdk.java.net/jdk/pull/7175/files/56503a5d..13648b7d

Webrevs:
 - full: https://webrevs.openjdk.java.net/?repo=jdk&pr=7175&range=01
 - incr: https://webrevs.openjdk.java.net/?repo=jdk&pr=7175&range=00-01

  Stats: 217 lines in 28 files changed: 148 ins; 35 del; 34 mod
  Patch: https://git.openjdk.java.net/jdk/pull/7175.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/7175/head:pull/7175

PR: https://git.openjdk.java.net/jdk/pull/7175