RFR: 8296419: [REDO] JDK-8295319: pending_cards_at_gc_start doesn't include cards in thread buffers [v3]

[Kim Barrett]

> Let's try this again.  This is the original JDK-8295319 change, plus a couple
> of small additions to fix problems with that original change.
> 
> The description of the original change was:
> 
> -----
> 
> 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 any buffers in the paused buffers lists.
> 
> -----
> 
> The problem was that by moving log concatenation earlier, it no longer
> followed the call to retire_tlabs().  Among other things, that function
> calls flush_deferred_card_mark_barrier() on each thread, possibly adding cards
> to the thread's dirty card queue.  Doing that after the log concatenation may
> lead to unprocessed cards in thread queues, with chaos ensuing.
> 
> To fix this, the call to retire_tlabs has also been moved, so that it once
> again precedes the log concatenation.  Also added (debug-only) verification
> that all thread dirty card queues are empty at the end of
> pre_evacuate_collection_set.
> 
> A possible followup is to refactor those two operations, which each do a
> (single-threaded) walk of all threads.  We could combine that into a single
> walk.  We could also parallelize it if that seems warranted, though the
> per-thread work is usually pretty small, so might not be worth parallelizing.
> 
> There might be an opportunity to do some similar refactoring for fullgc and
> log abandonment, though there the two operations are done far away from each
> other.
> 
> Testing:
> mach5 tier1-6

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 eight additional commits since the last revision:

 - Merge branch 'master' into cards-in-thread-buffers
 - fix typo
 - fix usage of _preserved_marks_set
 - rearrange pre-evacuation
 - Merge branch 'master' into cards-in-thread-buffers
 - retire tlabs before processing thread dcq
 - verify empty dirty card logs
 - Revert "8296414: [BACKOUT] JDK-8295319: pending_cards_at_gc_start doesn't include cards in thread buffers"
   
   This reverts commit b847fb687735ae5dff56d12d221556a5218b5bba.

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

Changes:
  - all: https://git.openjdk.org/jdk/pull/11053/files
  - new: https://git.openjdk.org/jdk/pull/11053/files/576e799c..70dfb138

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=11053&range=02
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=11053&range=01-02

  Stats: 26170 lines in 397 files changed: 11088 ins; 4913 del; 10169 mod
  Patch: https://git.openjdk.org/jdk/pull/11053.diff
  Fetch: git fetch https://git.openjdk.org/jdk pull/11053/head:pull/11053

PR: https://git.openjdk.org/jdk/pull/11053