[jdk16] RFR: 8258985: Parallel WeakProcessor may use too few threads [v3]

[Kim Barrett]

> Please review this fix to the parallel WeakProcessor's computation of the
> number of worker threads to use.  It was previously limited by the current
> value of active_workers(), whatever that happens to be.  It should be
> limited by total_workers(), just as with the parallel ReferenceProcessor.
> (Both are subject to ReferencesPerThread.)
> 
> Testing
> mach5 tier1
> Some hand testing (Linux-x64) to verify the expected number of threads are
> being used.
> 
> Note: That hand testing suggests some further tuning of ReferencesPerThread
> might be in order. With the current default of 1000, I often saw in testing
> that some threads were started late enough that no work was left for them.
> I'll file a separate RFE for that.

Kim Barrett 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 weak_ergo_workers
 - fix doc comments about number of threads used
 - Use total workers rather than active

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

Changes:
  - all: https://git.openjdk.java.net/jdk16/pull/75/files
  - new: https://git.openjdk.java.net/jdk16/pull/75/files/0ed088d8..e4bfea5c

Webrevs:
 - full: https://webrevs.openjdk.java.net/?repo=jdk16&pr=75&range=02
 - incr: https://webrevs.openjdk.java.net/?repo=jdk16&pr=75&range=01-02

  Stats: 4041 lines in 124 files changed: 1417 ins; 2424 del; 200 mod
  Patch: https://git.openjdk.java.net/jdk16/pull/75.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk16 pull/75/head:pull/75

PR: https://git.openjdk.java.net/jdk16/pull/75