RFR: 8295319: pending_cards_at_gc_start doesn't include cards in thread buffers [v2]

[Kim Barrett]

> Please review this change to G1 to include the per-thread buffers in the
> number of pending cards at the start of a young GC.
> 
> DCQS::concatenate_logs has been renamed to concatenate_logs_and_stats, and now
> also merges the per-thread refinement stats during the thread walk to flush
> buffers.  That replaces the separate thread walk to merge and record these
> stats earlier in the GC.  The merged stats and related info don't seem to be
> needed until after the buffer flushing.
> 
> Also, when abandoning dirty card buffers and stats because of a full GC, fixed
> to also abandon an buffers in the paused buffers lists.
> 
> Testing:
> mach5 tier1-3
> performance testing found no significant changes, as expected.

Kim Barrett has updated the pull request incrementally with one additional commit since the last revision:

  move per-thread dirty card log/stat concatenation earlier

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

Changes:
  - all: https://git.openjdk.org/jdk/pull/10914/files
  - new: https://git.openjdk.org/jdk/pull/10914/files/42e8681b..34a4b994

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=10914&range=01
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=10914&range=00-01

  Stats: 8 lines in 2 files changed: 3 ins; 3 del; 2 mod
  Patch: https://git.openjdk.org/jdk/pull/10914.diff
  Fetch: git fetch https://git.openjdk.org/jdk pull/10914/head:pull/10914

PR: https://git.openjdk.org/jdk/pull/10914