RFR: 8336742: Shenandoah: Add more verbose logging/stats for mark termination attempts [v6]

[Aleksey Shipilev]

On Tue, 13 Aug 2024 16:46:54 GMT, Neethu Prasad <nprasad at openjdk.org> wrote:

>> **Revision 2 Notes** 
>> 1. Added time spent on handshaking all threads requesting them to flush their SATB buffers as part of GC stats.
>> 2. As mentioned in PR feedback, will raise separate PR to adding logging in ShenandoahTimingsTracker.
>> 
>> **Revision 1 Notes**
>> This PR adds the following
>> 1.  info logging on number of SATB flush attempts
>> 3. total time spend on handshaking all threads requesting them to flush their SATB buffers.
>> 
>> As suggested by William in [JDK-8336742 ](https://bugs.openjdk.org/browse/JDK-83367420), we can use handshake logging to get time spend and other stats for each handshake.
>> 
>> [4.515s][info][handshake   ] Handshake "Shenandoah Flush SATB Handshake", Targeted threads: 1036, Executed by requesting thread: 1035, Total completion time: 597004 ns
>> [4.517s][info][handshake   ] Handshake "Shenandoah Flush SATB Handshake", Targeted threads: 1036, Executed by requesting thread: 1033, Total completion time: 207402 ns
>> 
>> 
>> **Testing**
>> 1. tier1, tier2 and hotspot_gc_shenandoah tests.
>> 2. **-Xlog:gc+stats=info**
>> 
>> 
>> [4.911s][info][gc,stats]   CMR: VM Strong Roots              539 us, workers (us): 102,  89,  89,  79,  46,  40,  40,  25,  24,   1,   2,   2, ---, ---, ---, ---, ---, ---, ---, ---, ---, ---, ---, ---, 
>> [4.911s][info][gc,stats]   CMR: CLDG Roots                   461 us, workers (us): 429,   5,  12,  11,   4, ---, ---, ---, ---, ---, ---, ---, ---, ---, ---, ---, ---, ---, ---, ---, ---, ---, ---, ---, 
>> [4.911s][info][gc,stats] Concurrent Marking                 4392 us
>> [4.911s][info][gc,stats]   Flush SATB                       1035 us
>> [4.911s][info][gc,stats] Pause Final Mark (G)               2615 us
>> [4.912s][info][gc,stats] Pause Final Mark (N)               2339 us
>> [4.912s][info][gc,stats]   Finish Mark                       780 us
>> [4.912s][info][gc,stats]   Update Region States              109 us
>> [4.912s][info][gc,stats]   Choose Collection Set            1336 us
>> [4.912s][info][gc,stats]   Rebuild Free Set                   23 us
>> 
>> 
>> on app termination
>> 
>> 
>> 4.924s][info][gc,stats] Concurrent Reset               =    0.042 s (a =     1846 us) (n =    23) (lvls, us =     1113,     1660,     1895,     2031,     2674)
>> [4.924s][info][gc,stats] Pause Init Mark (G)            =    0.073 s (a =     3163 us) (n =    23) (lvls, us =     2812,     2949,     3047,     3281,     3790)
>> [4.924s][info][gc,stats] Pause Init Mark (N)            =    0.065 s (a =     2810 us) (n =    23) ...
>
> Neethu Prasad has updated the pull request incrementally with one additional commit since the last revision:
> 
>   Fix indentation and naming

Marked as reviewed by shade (Reviewer).

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PR Review: https://git.openjdk.org/jdk/pull/20318#pullrequestreview-2236075482