[jdk17u-dev] RFR: 8350285: Shenandoah: Regression caused by ShenandoahLock under extreme contention [v2]

[Daniel Huang]

> 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 fix.

Daniel Huang has updated the pull request with a new target base due to a merge or a rebase. The incremental webrev excludes the unrelated changes brought in by the merge/rebase. The pull request contains three additional commits since the last revision:

 - Merge branch 'openjdk:master' into backport-JDK-8350285-shenandoahlock
 - Merge branch 'openjdk:master' into backport-JDK-8350285-shenandoahlock
 - Backport bd8ad309b59bceb3073a8d6411cca74e73508885

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Changes:
  - all: https://git.openjdk.org/jdk17u-dev/pull/3614/files
  - new: https://git.openjdk.org/jdk17u-dev/pull/3614/files/8188ec6e..469b7540

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk17u-dev&pr=3614&range=01
 - incr: https://webrevs.openjdk.org/?repo=jdk17u-dev&pr=3614&range=00-01

  Stats: 12461 lines in 465 files changed: 6412 ins; 4492 del; 1557 mod
  Patch: https://git.openjdk.org/jdk17u-dev/pull/3614.diff
  Fetch: git fetch https://git.openjdk.org/jdk17u-dev.git pull/3614/head:pull/3614

PR: https://git.openjdk.org/jdk17u-dev/pull/3614