8295319: pending_cards_at_gc_start doesn't include cards in thread buffers

[kimbarrett]

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.

---

Progress

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• Commit message must refer to an issue

Issue

• JDK-8295319: pending_cards_at_gc_start doesn't include cards in thread buffers

Reviewers

• Ivan Walulya (@walulyai - Reviewer) ⚠️ Review applies to 34a4b994
• Thomas Schatzl (@tschatzl - Reviewer) ⚠️ Review applies to 34a4b994

Reviewing

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Checkout this PR locally:
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$ git checkout pull/10914

Update a local copy of the PR:
$ git checkout pull/10914
$ git pull https://git.openjdk.org/jdk pull/10914/head

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Checkout this PR locally:
$ git pr checkout 10914

View PR using the GUI difftool:
$ git pr show -t 10914

Using diff file

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[bridgekeeper]

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[openjdk]

@kimbarrett The following label will be automatically applied to this pull request:

• hotspot-gc

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[mlbridge]

Webrevs

• 02: Full (b6099b83)
• 01: Full - Incremental (34a4b994)
• 00: Full (42e8681b)

[walulyai]

calculate_collection_set -> finalize_initial_collection_set -> finalize_young_part:
size_t pending_cards = _policy->pending_cards_at_gc_start() + _g1h->hot_card_cache()->num_entries();

called before pre_evacuate_collection_set

flush_dirty_card_logs_and_stats needs to be called before calculate_collection_set

[kimbarrett]

calculate_collection_set -> finalize_initial_collection_set -> finalize_young_part: size_t pending_cards = _policy->pending_cards_at_gc_start() + _g1h->hot_card_cache()->num_entries();

called before pre_evacuate_collection_set

flush_dirty_card_logs_and_stats needs to be called before calculate_collection_set

Sigh! Looks like I got lost while tracking down the callers and call chains.

So the use in finalize_young_part is presumably using the pending cards count from the previous
collection, which usually isn't such a bad value that it causes anything goes off the rails, so testing
didn't spot a problem.

I kind of hate some of that code, which has too many non-obvious and unchecked (and not easily
checked) ordering constraints.

Thanks for spotting this.

[kimbarrett]

calculate_collection_set -> finalize_initial_collection_set -> finalize_young_part: size_t pending_cards = _policy->pending_cards_at_gc_start() + _g1h->hot_card_cache()->num_entries();
called before pre_evacuate_collection_set
flush_dirty_card_logs_and_stats needs to be called before calculate_collection_set

Sigh! Looks like I got lost while tracking down the callers and call chains.

Fixed now.

[walulyai]

Lgtm!

[openjdk]

@kimbarrett This change now passes all automated pre-integration checks.

ℹ️ This project also has non-automated pre-integration requirements. Please see the file CONTRIBUTING.md for details.

After integration, the commit message for the final commit will be:

8295319: pending_cards_at_gc_start doesn't include cards in thread buffers

Reviewed-by: iwalulya, tschatzl

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[tschatzl]

Lgtm.

[openjdk]

@kimbarrett this pull request can not be integrated into master due to one or more merge conflicts. To resolve these merge conflicts and update this pull request you can run the following commands in the local repository for your personal fork:

git checkout cards-in-threads
git fetch https://git.openjdk.org/jdk master
git merge FETCH_HEAD
# resolve conflicts and follow the instructions given by git merge
git commit -m "Merge master"
git push

[kimbarrett]

Thanks @walulyai and @tschatzl for reviews.

[kimbarrett]

/integrate

[openjdk]

Going to push as commit 0349803.

[openjdk]

@kimbarrett Pushed as commit 0349803.

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