8268122: Add specific gc cause for G1 full collections

[kstefanj]

Please review this change to add a new GC cause for GC Full collections that are caused by a prior collection not being able to free up enough space.

Summary
During the review of PR #3143 it got pretty clear that reusing the Young GC cause for a following Full GC is not always good. A solution for this is to add a new GC cause that is used if a young collection can't free up enough space. This cause will not be used for other explicit Full GCs, like a call to System.gc().

The would result in a change from:

[13,276s][info][gc             ] GC(71) Pause Young (Normal) (G1 Evacuation Pause) 3096M->3096M(3100M) 1,159ms
[13,644s][info][gc             ] GC(72) Pause Full (G1 Evacuation Pause) 3096M->3096M(3100M) 368,157ms

to:

[18,454s][info][gc             ] GC(84) Pause Young (Normal) (G1 Evacuation Pause) 3096M->3096M(3100M) 1,312ms
[18,815s][info][gc             ] GC(85) Pause Full (G1 Compaction Pause) 3096M->3096M(3100M) 360,737ms

This PR is currently based in PR #4342, where we slightly change how Full GCs are scheduled if a Younc GC can't free up enough space.

Testing
I've tested this change together with PR #4342 and tier1-3 looks good. Also done manual testing making sure the GC-cause is used correctly.

---

Progress

• Change must not contain extraneous whitespace
• Commit message must refer to an issue
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Issue

• JDK-8268122: Add specific gc cause for G1 full collections

Reviewers

• Thomas Schatzl (@tschatzl - Reviewer) ⚠️ Review applies to afaf3ef
• Kim Barrett (@kimbarrett - Reviewer) ⚠️ Review applies to 1f35757

Reviewing

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$ git checkout pull/4357

Update a local copy of the PR:
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$ git pull https://git.openjdk.java.net/jdk pull/4357/head

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$ git pr checkout 4357

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https://git.openjdk.java.net/jdk/pull/4357.diff

[bridgekeeper]

👋 Welcome back sjohanss! A progress list of the required criteria for merging this PR into pr/4342 will be added to the body of your pull request. There are additional pull request commands available for use with this pull request.

[openjdk]

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

• hotspot-gc

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[mlbridge]

Webrevs

• 03: Full (7f0c714d)
• 02: Full - Incremental (1f357578)
• 01: Full - Incremental (afaf3efe)
• 00: Full (4eabb975)

[tschatzl]

Lgtm.

Pre-existing: The two changed tests seem to be exactly the same....

[kstefanj]

Lgtm.

Pre-existing: The two changed tests seem to be exactly the same....

The "G1ConcurrentMark" test is run with -XX:+ExplicitGCInvokesConcurrent so there is a small difference in that we will get an explicit young GC with System.gc() as the cause.

I just pushed a small change to move the new cause up to under the "G1 Evacuation Pause" in the enum.

[kimbarrett]

Looks good.

[openjdk-notifier]

The dependent pull request has now been integrated, and the target branch of this pull request has been updated. This means that changes from the dependent pull request can start to show up as belonging to this pull request, which may be confusing for reviewers. To remedy this situation, simply merge the latest changes from the new target branch into this pull request by running commands similar to these in the local repository for your personal fork:

git checkout 8268163-full-gc-order
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# if there are conflicts, follow the instructions given by git merge
git commit -m "Merge master"
git push

[openjdk]

@kstefanj 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 8268122-gc-cause
git fetch https://git.openjdk.java.net/jdk master
git merge FETCH_HEAD
# resolve conflicts and follow the instructions given by git merge
git commit -m "Merge master"
git push

[openjdk]

@kstefanj 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:

8268122: Add specific gc cause for G1 full collections

Reviewed-by: tschatzl, kbarrett

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At the time when this comment was updated there had been 1 new commit pushed to the master branch:

• 43e38a1: 8268377: Windows 32bit build fails after JDK-8268174

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[kstefanj]

Thanks @tschatzl and @kimbarrett for the reviews.

/integrate

[openjdk]

@kstefanj Since your change was applied there has been 1 commit pushed to the master branch:

• 43e38a1: 8268377: Windows 32bit build fails after JDK-8268174

Your commit was automatically rebased without conflicts.

Pushed as commit caf7f49.

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