[jdk17u-dev] Integrated: 8325754: Dead AbstractQueuedSynchronizer$ConditionNodes survive minor garbage collections

[Neethu Prasad]

On Mon, 17 Jun 2024 22:14:40 GMT, Neethu Prasad <nprasad at openjdk.org> wrote:

> **Notes**
> Backport of [JDK-8325754](https://bugs.openjdk.org/browse/JDK-8325754).
> 
> Unlink 'ConditionNode' before they are transferred to the sync queue as G1 seems to be able to collect “dead” ConditionNode instances during minor collections only if no formerly alive ConditionNode instances were promoted to the old generation and died there, which often cannot be avoided since e.g. on application startup many objects are promoted to the old generation after a few collections.
> 
> **Verification**
> 
> * jdk_util, Tier 1 & Tier 2 tests passed.
> * Ran G1LoiteringConditionNodes.java (sample code from bug description) and verified that YG GC time is not increasing after full GC.
> 
> _Before PR_
> 
> 
> dev-dsk-neethp-jdk-2c-ad54955c % /home/neethp/Development/jdk17u-dev/build/linux-x86_64-server-release/images/jdk/bin/java -Xms2048m -Xmx2048m -XX:+UseG1GC -XX:+UnlockExperimentalVMOptions -XX:G1MaxNewSizePercent=20 '-Xlog:gc*,gc+age*=trace' -cp . G1LoiteringConditionNodes | grep -E 'Pause.*ms'
> [0.960s][info ][gc          ] GC(0) Pause Young (Normal) (G1 Evacuation Pause) 102M->1M(2048M) 5.290ms
> [2.485s][info ][gc          ] GC(1) Pause Young (Normal) (G1 Evacuation Pause) 149M->1M(2048M) 2.288ms
> [6.805s][info ][gc          ] GC(2) Pause Young (Normal) (G1 Evacuation Pause) 409M->1M(2048M) 2.393ms
> [11.165s][info ][gc          ] GC(3) Pause Young (Normal) (G1 Evacuation Pause) 409M->1M(2048M) 2.603ms
> [15.544s][info ][gc          ] GC(4) Pause Young (Normal) (G1 Evacuation Pause) 409M->1M(2048M) 2.462ms
> [19.955s][info ][gc          ] GC(5) Pause Young (Normal) (G1 Evacuation Pause) 409M->1M(2048M) 2.382ms
> [24.369s][info ][gc          ] GC(6) Pause Young (Normal) (G1 Evacuation Pause) 409M->1M(2048M) 2.246ms
> [28.790s][info ][gc          ] GC(7) Pause Young (Normal) (G1 Evacuation Pause) 409M->1M(2048M) 2.443ms
> [33.211s][info ][gc          ] GC(8) Pause Young (Normal) (G1 Evacuation Pause) 409M->1M(2048M) 2.331ms
> [37.639s][info ][gc          ] GC(9) Pause Young (Normal) (G1 Evacuation Pause) 409M->1M(2048M) 2.319ms
> [42.066s][info ][gc          ] GC(10) Pause Young (Normal) (G1 Evacuation Pause) 409M->1M(2048M) 2.629ms
> [46.515s][info ][gc          ] GC(11) Pause Young (Normal) (G1 Evacuation Pause) 409M->1M(2048M) 2.334ms
> [50.957s][info ][gc          ] GC(12) Pause Young (Normal) (G1 Evacuation Pause) 409M->1M(2048M) 2.280ms
> [55.382s][info ][gc          ] GC(13) Pause Young (Normal) (G1 Evacuation Pause) 409M->1M(2048M) 2.413ms
> [59.830s][info ][gc          ] GC(14) Pause Young (Norma...

This pull request has now been integrated.

Changeset: 4c58e1b5
Author:    Neethu Prasad <nprasad at openjdk.org>
Committer: Paul Hohensee <phh at openjdk.org>
URL:       https://git.openjdk.org/jdk17u-dev/commit/4c58e1b5a0f6ba07729fdf96bce07441c927898f
Stats:     10 lines in 2 files changed: 10 ins; 0 del; 0 mod

8325754: Dead AbstractQueuedSynchronizer$ConditionNodes survive minor garbage collections

Backport-of: 60cbf2925024b1c2253256688ae41741fff0a860

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PR: https://git.openjdk.org/jdk17u-dev/pull/2599