8271163: G1 uses wrong degree of MT processing since JDK-8270169

[tschatzl]

Hi all,

JDK-8270169 changed the amount of resources supplied by the CM reference processor, assuming that the CM ref processor is only ever used with the marking threads.
This is unfortunately not true, the CM reference processor is also used by the Remark pause for discovery using the parallel gc worker threads.

This causes crashes because of the code assuming single threaded operation while it is not.

The solution proposed here is to just revert JDK-8270169 which introduced that change. Applies cleanly.

I also added a comment in the reference processor constructor to why we need to consider both thread counts.

Thanks,
Thomas

---

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Issue

• JDK-8271163: G1 uses wrong degree of MT processing since JDK-8270169

Reviewers

• Kim Barrett (@kimbarrett - Reviewer)
• Albert Mingkun Yang (@albertnetymk - Committer)

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• 01: Full - Incremental (04e043a2)
• 00: Full (c7628e64)

[kimbarrett]

Looks good.

[openjdk]

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

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

8271163: G1 uses wrong degree of MT processing since JDK-8270169

Reviewed-by: kbarrett, ayang

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At the time when this comment was updated there had been 2 new commits pushed to the master branch:

• 8a789b7: 8263840: PeriodicTask should declare its destructor virtual
• f226190: 8270894: Use acquire semantics in ObjectSynchronizer::read_stable_mark()

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[kimbarrett]

As this is a simple backout (plus commentary), I suggest not waiting the usual 24 hours before pushing, to reduce testing noise.

[tschatzl]

Since this is basically a clean backout of JDK-8270169, I'll skip the 24h rule requirement.

Thanks @kimbarrett @albertnetymk for your reviews.

/integrate

[openjdk]

Going to push as commit 8c8e3a0.
Since your change was applied there have been 2 commits pushed to the master branch:

• 8a789b7: 8263840: PeriodicTask should declare its destructor virtual
• f226190: 8270894: Use acquire semantics in ObjectSynchronizer::read_stable_mark()

Your commit was automatically rebased without conflicts.

[openjdk]

@tschatzl Pushed as commit 8c8e3a0.

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