8304341: [Lilliput] Use fixed-size lock-stack

[rkennke]

Until now, we used to have a variable-sized lock-stack: when pushing an object to it and capacity is exceeded, it would re-allocate a new stack and use that. However, experiments show that the lock-stack very rarely exceeds 5 slots (I have not yet found a workload that does actually exceed it). It makes sense to make the lock-stack a fixed-size array: it makes addressing the lock-stack simpler and more efficient and it increases the likelyhood of the lock-stack being in CPU cache. If the lock-stack is ever exceeded, we would not do stack-locking at all, but instead inflate the monitor and use that.

This is already integrated in the related upstream PR: openjdk/jdk#10907

Testing:

• tier1
• tier2

---

Progress

• Change must not contain extraneous whitespace
• Commit message must refer to an issue
• Change must be properly reviewed (1 review required, with at least 1 Committer)

Integration blocker

 ⚠️ Whitespace errors (failed with the updated jcheck configuration)

Issue

• JDK-8304341: [Lilliput] Use fixed-size lock-stack (Enhancement - P4)

Reviewers

• Aleksey Shipilev (@shipilev - Committer)

Reviewing

Using git

Checkout this PR locally:
$ git fetch https://git.openjdk.org/lilliput.git pull/81/head:pull/81
$ git checkout pull/81

Update a local copy of the PR:
$ git checkout pull/81
$ git pull https://git.openjdk.org/lilliput.git pull/81/head

Using Skara CLI tools

Checkout this PR locally:
$ git pr checkout 81

View PR using the GUI difftool:
$ git pr show -t 81

Using diff file

Download this PR as a diff file:
https://git.openjdk.org/lilliput/pull/81.diff

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[bridgekeeper]

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[mlbridge]

Webrevs

• 01: Full - Incremental (7824614a)
• 00: Full (3e0392b9)

[shipilev]

I guess there is nothing actually to review here, and the comments should be added to openjdk/jdk#10907. I skimmed through the changes and there are no evident problems with it.

[openjdk]

@rkennke This change is no longer ready for integration - check the PR body for details.

[openjdk]

@rkennke 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 JDK-8304341
git fetch https://git.openjdk.org/lilliput.git master
git merge FETCH_HEAD
# resolve conflicts and follow the instructions given by git merge
git commit -m "Merge master"
git push