RFR: 8350314: Shenandoah: Capture thread state sync times in GC timings [v2]

[Xiaolong Peng]

> The change is to improve the observability of  Shenandoah GC, basically there are two changes for  Shenandoah GC timings in this PR:
> 
> 1. Net GC pause timings include the time to propagate GC state to Java threads
> 2. Add new timing "Propagate GC state" in Shenandoah GC timing logs
> 
> With the change, the new GC timing log will be like:
> 
> [11.056s][info][gc,stats    ] Concurrent Reset                     89 us
> [11.056s][info][gc,stats    ] Pause Init Mark (G)                 257 us
> [11.056s][info][gc,stats    ] Pause Init Mark (N)                  17 us
> [11.056s][info][gc,stats    ]   Update Region States                3 us
> [11.056s][info][gc,stats    ]   Propagate GC state                  1 us
> [11.056s][info][gc,stats    ] Concurrent Mark Roots               232 us, parallelism: 1.96x
> [11.056s][info][gc,stats    ]   CMR: <total>                      456 us
> [11.056s][info][gc,stats    ]   CMR: Thread Roots                 429 us, workers (us): 139, 148, 142, ---, ---, ---, 
> [11.057s][info][gc,stats    ]   CMR: VM Strong Roots               11 us, workers (us):   8,   3,   0, ---, ---, ---, 
> [11.057s][info][gc,stats    ]   CMR: CLDG Roots                    16 us, workers (us):  16, ---, ---, ---, ---, ---, 
> [11.057s][info][gc,stats    ] Concurrent Marking                 1304 us, parallelism: 2.33x
> [11.057s][info][gc,stats    ]   CM: <total>                      3043 us
> [11.057s][info][gc,stats    ]   CM: Parallel Mark                3043 us, workers (us): 1023, 1017, 1003, ---, ---, ---, 
> [11.057s][info][gc,stats    ]   Flush SATB                        204 us
> [11.057s][info][gc,stats    ] Pause Final Mark (G)                865 us
> [11.057s][info][gc,stats    ] Pause Final Mark (N)                234 us
> [11.057s][info][gc,stats    ]   Finish Mark                       129 us, parallelism: 0.01x
> [11.057s][info][gc,stats    ]   Propagate GC state                  2 us
> [11.057s][info][gc,stats    ]   Update Region States               12 us
> [11.057s][info][gc,stats    ]   Choose Collection Set              25 us
> [11.057s][info][gc,stats    ]   Rebuild Free Set                   29 us
> [11.057s][info][gc,stats    ] Concurrent Weak References           67 us, parallelism: 0.25x
> [11.057s][info][gc,stats    ]   CWRF: <total>                      17 us
> [11.057s][info][gc,stats    ]   CWRF: Weak References              17 us, workers (us):  15,   1,   0, ---, ---, ---, 
> [11.057s][info][gc,stats    ] Concurrent Weak Roots               413 us
> [11.057s][info][gc,stats  ...

Xiaolong Peng has updated the pull request incrementally with one additional commit since the last revision:

  Address review comments

-------------

Changes:
  - all: https://git.openjdk.org/jdk/pull/23759/files
  - new: https://git.openjdk.org/jdk/pull/23759/files/4940e451..cad4a434

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=23759&range=01
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=23759&range=00-01

  Stats: 7 lines in 3 files changed: 0 ins; 0 del; 7 mod
  Patch: https://git.openjdk.org/jdk/pull/23759.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/23759/head:pull/23759

PR: https://git.openjdk.org/jdk/pull/23759