Integrated: 8345423: Shenandoah: Parallelize concurrent cleanup

[Xiaolong Peng]

On Wed, 4 Dec 2024 08:25:40 GMT, Xiaolong Peng <xpeng at openjdk.org> wrote:

> Concurrent cleanup after Shenandoah collection cycle is executed by single thread(Shenandoah control thread), since currently recycling trashed regions requires heap lock even it can be done w/o heap lock. This PR is a proposal to parallelize the execution of Shenandoah concurrent cleanup after making recycling trashed regions lock free. 
> 
> With the change the time execute Concurrent cleanup has been significantly improved by 10+ times, throughput/allocation rate is also improved significantly:
> 
> TIP:
> 
> [30.380s][info][gc] GC(1245) Concurrent cleanup (Young) 3491M->739M(4096M) 3.634ms
> [30.404s][info][gc] GC(1246) Concurrent cleanup (Young) 3258M->377M(4096M) 2.233ms
> [30.434s][info][gc] GC(1247) Concurrent cleanup (Young) 2887M->333M(4096M) 7.958ms
> [30.464s][info][gc] GC(1248) Concurrent cleanup (Young) 3134M->472M(4096M) 6.097ms
> [30.487s][info][gc] GC(1249) Concurrent cleanup (Young) 2922M->212M(4096M) 3.072ms
> [30.519s][info][gc] GC(1250) Concurrent cleanup (Young) 3404M->549M(4096M) 3.730ms
> [30.552s][info][gc] GC(1251) Concurrent cleanup (Young) 3542M->712M(4096M) 6.118ms
> [30.579s][info][gc] GC(1252) Concurrent cleanup (Young) 3257M->373M(4096M) 5.049ms
> [30.608s][info][gc] GC(1253) Concurrent cleanup (Young) 3390M->418M(4096M) 2.779ms
> 
> Parallelized:
> 
> [30.426s][info][gc] GC(1557) Concurrent cleanup (Young) 3208M->43M(4096M) 0.177ms
> [30.510s][info][gc] GC(1560) Concurrent cleanup (Young) 2938M->161M(4096M) 0.220ms
> [30.534s][info][gc] GC(1561) Concurrent cleanup (Young) 2960M->57M(4096M) 0.164ms
> [30.564s][info][gc] GC(1562) Concurrent cleanup (Young) 3189M->106M(4096M) 0.176ms
> [30.595s][info][gc] GC(1563) Concurrent cleanup (Young) 3389M->367M(4096M) 0.247ms
> [30.625s][info][gc] GC(1564) Concurrent cleanup (Young) 3662M->628M(4096M) 0.246ms
> [30.649s][info][gc] GC(1565) Concurrent cleanup (Young) 3190M->150M(4096M) 0.172ms
> [30.678s][info][gc] GC(1566) Concurrent cleanup (Young) 3225M->69M(4096M) 0.175ms
> [30.709s][info][gc] GC(1567) Concurrent cleanup (Young) 3250M->107M(4096M) 0.179ms
> [30.765s][info][gc] GC(1570) Concurrent cleanup (Young) 2932M->211M(4096M) 0.422ms
> 
> 
> JVM args for the tests: `-Xms4G -Xmx4G -XX:+AlwaysPreTouch -XX:+UseShenandoahGC -XX:+UnlockExperimentalVMOptions -XX:ShenandoahGCMode=generational -XX:-ShenandoahPacing -XX:+UseTLAB -Xlog:gc`
> 
> 
> For the same test test, but with large heap with 32G memory, the improvement on concurrent cleanup is much smaller, which might be related to less race and contention with mutator threads when the heap size i...

This pull request has now been integrated.

Changeset: 4da6fd42
Author:    Xiaolong Peng <xpeng at openjdk.org>
URL:       https://git.openjdk.org/jdk/commit/4da6fd4283a13be1711e7ad948f1d05a0a9148a5
Stats:     228 lines in 13 files changed: 79 ins; 56 del; 93 mod

8345423: Shenandoah: Parallelize concurrent cleanup

Reviewed-by: ysr, kdnilsen, wkemper

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PR: https://git.openjdk.org/jdk/pull/22538