RFR: 8352185: Shenandoah: Invalid logic for remembered set verification [v13]

[Y. Srinivas Ramakrishna]

On Fri, 21 Mar 2025 15:08:22 GMT, Xiaolong Peng <xpeng at openjdk.org> wrote:

>> I was suggesting looking to see if normal perf measures showed any improvements. E.g. if you ran say SPECjbb and compared the remset scan times for the minor GC's that followed global collections.
>
> I have run h2 benchmark, here is the remembered set scan times after a global GC, it does seem to improve  remembered set scan time in this case:
> 
> PR version:
> 
> [2025-03-21T07:35:41.801+0000][10.292s][19715][info ][gc             ] GC(6) Concurrent remembered set scanning 13.069ms
> [2025-03-21T07:35:48.088+0000][16.579s][19715][info ][gc             ] GC(9) Concurrent remembered set scanning 5.537ms
> [2025-03-21T07:35:56.610+0000][25.101s][19715][info ][gc             ] GC(14) Concurrent remembered set scanning 6.186ms
> [2025-03-21T07:36:03.967+0000][32.459s][19715][info ][gc             ] GC(18) Concurrent remembered set scanning 9.562ms
> [2025-03-21T07:36:11.234+0000][39.725s][19715][info ][gc             ] GC(22) Concurrent remembered set scanning 2.591ms
> [2025-03-21T07:36:17.303+0000][45.794s][19715][info ][gc             ] GC(25) Concurrent remembered set scanning 0.999ms
> [2025-03-21T07:36:25.647+0000][54.139s][19715][info ][gc             ] GC(30) Concurrent remembered set scanning 1.665ms
> [2025-03-21T07:36:32.790+0000][61.281s][19715][info ][gc             ] GC(33) Concurrent remembered set scanning 2.851ms
> [2025-03-21T07:36:40.241+0000][68.732s][19715][info ][gc             ] GC(36) Concurrent remembered set scanning 0.716ms
> [2025-03-21T07:36:47.440+0000][75.931s][19715][info ][gc             ] GC(39) Concurrent remembered set scanning 1.932ms
> 
> 
> master:
> 
> [2025-03-21T07:34:04.978+0000][10.765s][17923][info ][gc             ] GC(6) Concurrent remembered set scanning 22.813ms
> [2025-03-21T07:34:11.250+0000][17.038s][17923][info ][gc             ] GC(9) Concurrent remembered set scanning 14.457ms
> [2025-03-21T07:34:18.692+0000][24.480s][17923][info ][gc             ] GC(14) Concurrent remembered set scanning 4.972ms
> [2025-03-21T07:34:26.033+0000][31.820s][17923][info ][gc             ] GC(18) Concurrent remembered set scanning 9.134ms
> [2025-03-21T07:34:34.416+0000][40.203s][17923][info ][gc             ] GC(22) Concurrent remembered set scanning 3.655ms
> [2025-03-21T07:34:42.180+0000][47.967s][17923][info ][gc             ] GC(26) Concurrent remembered set scanning 3.253ms
> [2025-03-21T07:34:49.371+0000][55.168s][17923][info ][gc             ] GC(29) Concurrent remembered set scanning 1.615ms
> [2025-03-21T07:34:56.592+0000][62.396s][17923][info ][gc             ] GC(32) Concurrent remembered set scanning 1.570ms
> [2025-03-21T07:35:03.766+0000][69.575s][17923][info ][gc             ] GC(35) Concurrent remembered set scanning 1.040ms
> [2025-03-21T07:35:10.941+0000][...

very cool!

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PR Review Comment: https://git.openjdk.org/jdk/pull/24092#discussion_r2013099621