8350285: Shenandoah: Regression caused by ShenandoahLock under extreme contention

[dtmhuang]

Backport for ShenandoahLock performance regression issue. The fix involves sleeping for a very short duration every 3 yields, with the number of yields picked through manual testing.

Clean backport, ran GHA sanity checks and locally tested tier1, tier2, and hotspot_gc_shenandoah. test/jdk/java/nio/channels/FileChannel/directio/DirectIOTest.java sometimes fails locally, but it also sometimes failed before the backport.

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Progress

• Change must not contain extraneous whitespace
• Commit message must refer to an issue
• JDK-8350285 needs maintainer approval

Issue

• JDK-8350285: Shenandoah: Regression caused by ShenandoahLock under extreme contention (Bug - P4 - Requested)

Reviewing

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[openjdk]

❗ This change is not yet ready to be integrated.
See the Progress checklist in the description for automated requirements.

[openjdk]

This backport pull request has now been updated with issue from the original commit.

[dtmhuang]

/covered

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[shipilev]

Just to make sure, @robilad: @dtmhuang is from Amazon :)

[openjdk]

⚠️ @dtmhuang This change is now ready for you to apply for maintainer approval. This can be done directly in each associated issue or by using the /approval command.

[mlbridge]

Webrevs

• 01: Full - Incremental (469b7540)
• 00: Full (8188ec6e)

[dtmhuang]

/approval request for backport of JDK-8350285 Shenandoah: Regression caused by ShenandoahLock under extreme contention

Motivation: Without this change, ShenandoahLock has some performance regression

Risk: Low. Ran GHA Sanity Checks, and tier 1 and tier 2 tests locally. Patch is clean. Change has been present in tip since February, 2025.

[openjdk]

@dtmhuang
8350285: The approval request has been created successfully.